diff --git a/mps/code/arenacl.c b/mps/code/arenacl.c
index db10accd6fe..d0e65a53ac1 100644
--- a/mps/code/arenacl.c
+++ b/mps/code/arenacl.c
@@ -216,19 +216,11 @@ static Res ClientArenaInit(Arena *arenaReturn, ArenaClass class, ArgList args)
   AVER(arenaReturn != NULL);
   AVER((ArenaClass)mps_arena_class_cl() == class);
   AVER(ArgListCheck(args));
-
-  if (ArgPick(&arg, args, MPS_KEY_ARENA_SIZE)) {
-    size = arg.val.size;
-    if (ArgPick(&arg, args, MPS_KEY_ARENA_CL_ADDR))
-      base = arg.val.addr;
-    else {
-      res = ResPARAM;
-      goto failParam;
-    }
-  } else {
-    res = ResPARAM;
-    goto failParam;
-  }
+  
+  ArgRequire(&arg, args, MPS_KEY_ARENA_SIZE);
+  size = arg.val.size;
+  ArgRequire(&arg, args, MPS_KEY_ARENA_CL_ADDR);
+  base = arg.val.addr;
 
   AVER(base != (Addr)0);
 
@@ -272,7 +264,7 @@ static Res ClientArenaInit(Arena *arenaReturn, ArenaClass class, ArgList args)
 
 failChunkCreate:
   ArenaFinish(arena);
-failParam:
+  AVER(res != ResOK);
   return res;
 }
 
diff --git a/mps/code/arenavm.c b/mps/code/arenavm.c
index 0bb83500f25..9904ada470a 100644
--- a/mps/code/arenavm.c
+++ b/mps/code/arenavm.c
@@ -478,12 +478,8 @@ static Res VMArenaInit(Arena *arenaReturn, ArenaClass class, ArgList args)
   AVER(class == VMArenaClassGet() || class == VMNZArenaClassGet());
   AVER(ArgListCheck(args));
 
-  if (ArgPick(&arg, args, MPS_KEY_ARENA_SIZE))
-    userSize = arg.val.size;
-  else {
-    res = ResPARAM;
-    goto failVMCreate;
-  }
+  ArgRequire(&arg, args, MPS_KEY_ARENA_SIZE);
+  userSize = arg.val.size;
 
   AVER(userSize > 0);
   
diff --git a/mps/code/arg.c b/mps/code/arg.c
index 4d2447e5c00..14170c3ed35 100644
--- a/mps/code/arg.c
+++ b/mps/code/arg.c
@@ -142,6 +142,15 @@ found:
 }
 
 
+/* ArgRequire -- take a required argument out of the argument list by keyword */
+
+void ArgRequire(ArgStruct *argOut, ArgList args, Key key) {
+  if (ArgPick(argOut, args, key))
+    return;
+  NOTREACHED;
+}
+
+
 /* C. COPYRIGHT AND LICENSE
  *
  * Copyright (C) 2001-2013 Ravenbrook Limited <http://www.ravenbrook.com/>.
diff --git a/mps/code/arg.h b/mps/code/arg.h
index 2647937c201..dc1e8a2a991 100644
--- a/mps/code/arg.h
+++ b/mps/code/arg.h
@@ -37,7 +37,7 @@ extern Bool ArgCheck(Arg arg);
 extern Bool ArgListCheck(ArgList args);
 
 extern Bool ArgPick(ArgStruct *argOut, ArgList args, Key key);
-extern void ArgRequired(ArgStruct *argOut, ArgList args, Key key);
+extern void ArgRequire(ArgStruct *argOut, ArgList args, Key key);
 
 extern Bool ArgCheckCant(Arg arg);
 extern Bool ArgCheckFormat(Arg arg);
diff --git a/mps/code/dbgpool.c b/mps/code/dbgpool.c
index d70e855adc3..88dec0532b6 100644
--- a/mps/code/dbgpool.c
+++ b/mps/code/dbgpool.c
@@ -132,12 +132,8 @@ static Res DebugPoolInit(Pool pool, ArgList args)
 
   /* TODO: Split this structure into separate keyword arguments,
      now that we can support them. */
-  if (ArgPick(&arg, args, MPS_KEY_POOL_DEBUG_OPTIONS))
-    options = (PoolDebugOptions)arg.val.pool_debug_options;
-  else {
-    res = ResPARAM;
-    goto failParam;
-  }
+  ArgRequire(&arg, args, MPS_KEY_POOL_DEBUG_OPTIONS);
+  options = (PoolDebugOptions)arg.val.pool_debug_options;
   
   AVERT(PoolDebugOptions, options);
 
@@ -208,7 +204,7 @@ static Res DebugPoolInit(Pool pool, ArgList args)
 tagFail:
 alignFail:
   SuperclassOfPool(pool)->finish(pool);
-failParam:
+  AVER(res != ResOK);
   return res;
 }
 
diff --git a/mps/code/poolamc.c b/mps/code/poolamc.c
index 8235b66c05f..b6b4e5c0289 100644
--- a/mps/code/poolamc.c
+++ b/mps/code/poolamc.c
@@ -973,9 +973,9 @@ static Res amcInitComm(Pool pool, RankSet rankSet, ArgList args)
   amc = Pool2AMC(pool);
   arena = PoolArena(pool);
 
-  ArgRequired(&arg, args, MPS_KEY_FORMAT);
+  ArgRequire(&arg, args, MPS_KEY_FORMAT);
   pool->format = arg.val.format;
-  ArgRequired(&arg, args, MPS_KEY_CHAIN);
+  ArgRequire(&arg, args, MPS_KEY_CHAIN);
   amc->chain = arg.val.chain;
   
   AVERT(Format, pool->format);
diff --git a/mps/code/poolams.c b/mps/code/poolams.c
index 6d4b8615abf..e5e4b249bcb 100644
--- a/mps/code/poolams.c
+++ b/mps/code/poolams.c
@@ -769,24 +769,12 @@ static Res AMSInit(Pool pool, ArgList args)
   AVERT(Pool, pool);
   AVER(ArgListCheck(args));
 
-  if (ArgPick(&arg, args, MPS_KEY_CHAIN))
-    chain = arg.val.chain;
-  else {
-    res = ResPARAM;
-    goto failParam;
-  }
-  if (ArgPick(&arg, args, MPS_KEY_FORMAT))
-    format = arg.val.format;
-  else {
-    res = ResPARAM;
-    goto failParam;
-  }
-  if (ArgPick(&arg, args, MPS_KEY_AMS_SUPPORT_AMBIGUOUS))
-    supportAmbiguous = arg.val.b;
-  else {
-    res = ResPARAM;
-    goto failParam;
-  }
+  ArgRequire(&arg, args, MPS_KEY_CHAIN);
+  chain = arg.val.chain;
+  ArgRequire(&arg, args, MPS_KEY_FORMAT);
+  format = arg.val.format;
+  ArgRequire(&arg, args, MPS_KEY_AMS_SUPPORT_AMBIGUOUS);
+  supportAmbiguous = arg.val.b;
 
   /* .ambiguous.noshare: If the pool is required to support ambiguous */
   /* references, the alloc and white tables cannot be shared. */
@@ -795,9 +783,6 @@ static Res AMSInit(Pool pool, ArgList args)
     EVENT3(PoolInitAMS, pool, PoolArena(pool), format);
   }
   return res;
-
-failParam:
-  return res;
 }
 
 
diff --git a/mps/code/poolawl.c b/mps/code/poolawl.c
index 95534d66958..96f0d2bef03 100644
--- a/mps/code/poolawl.c
+++ b/mps/code/poolawl.c
@@ -541,18 +541,10 @@ static Res AWLInit(Pool pool, ArgList args)
 
   awl = Pool2AWL(pool);
   
-  if (ArgPick(&arg, args, MPS_KEY_FORMAT))
-    format = arg.val.format;
-  else {
-    res = ResPARAM;
-    goto failParam;
-  }
-  if (ArgPick(&arg, args, MPS_KEY_AWL_FIND_DEPENDENT))
-    findDependent = (FindDependentMethod)arg.val.addr_method;
-  else {
-    res = ResPARAM;
-    goto failParam;
-  }
+  ArgRequire(&arg, args, MPS_KEY_FORMAT);
+  format = arg.val.format;
+  ArgRequire(&arg, args, MPS_KEY_AWL_FIND_DEPENDENT);
+  findDependent = (FindDependentMethod)arg.val.addr_method;
 
   AVERT(Format, format);
   pool->format = format;
@@ -584,7 +576,7 @@ static Res AWLInit(Pool pool, ArgList args)
 
 failGenInit:
   ChainDestroy(chain);
-failParam:
+  AVER(res != ResOK);
   return res;
 }
 
diff --git a/mps/code/poollo.c b/mps/code/poollo.c
index 541f0901781..8943f37c8ba 100644
--- a/mps/code/poollo.c
+++ b/mps/code/poollo.c
@@ -493,12 +493,8 @@ static Res LOInit(Pool pool, ArgList args)
 
   arena = PoolArena(pool);
   
-  if (ArgPick(&arg, args, MPS_KEY_FORMAT))
-    format = arg.val.format;
-  else {
-    res = ResPARAM;
-    goto failParam;
-  }
+  ArgRequire(&arg, args, MPS_KEY_FORMAT);
+  format = arg.val.format;
   
   AVERT(Format, format);
 
@@ -525,7 +521,7 @@ static Res LOInit(Pool pool, ArgList args)
 
 failGenInit:
   ChainDestroy(lo->chain);
-failParam:
+  AVER(res != ResOK);
   return res;
 }
 
diff --git a/mps/code/poolmfs.c b/mps/code/poolmfs.c
index 4a33ed050a1..538be571934 100644
--- a/mps/code/poolmfs.c
+++ b/mps/code/poolmfs.c
@@ -93,8 +93,8 @@ ARG_DEFINE_KEY(mfs_unit_size, Size);
 
 static Res MFSInit(Pool pool, ArgList args)
 {
-  Res res;
-  Size extendBy, unitSize;
+  Size extendBy = MFS_EXTEND_BY_DEFAULT;
+  Size unitSize;
   MFS mfs;
   Arena arena;
   ArgStruct arg;
@@ -102,16 +102,11 @@ static Res MFSInit(Pool pool, ArgList args)
   AVER(pool != NULL);
   AVER(ArgListCheck(args));
   
-  if (ArgPick(&arg, args, MPS_KEY_MFS_UNIT_SIZE))
-    unitSize = arg.val.size;
-  else {
-    res = ResPARAM;
-    goto failParam;
-  }
+  ArgRequire(&arg, args, MPS_KEY_MFS_UNIT_SIZE);
+  unitSize = arg.val.size;
   if (ArgPick(&arg, args, MPS_KEY_EXTEND_BY))
     extendBy = arg.val.size;
   else {
-    extendBy = MFS_EXTEND_BY_DEFAULT;
     if (extendBy < unitSize)
       extendBy = unitSize;
   }
@@ -137,9 +132,6 @@ static Res MFSInit(Pool pool, ArgList args)
   AVERT(MFS, mfs);
   EVENT4(PoolInitMFS, pool, arena, extendBy, unitSize);
   return ResOK;
-
-failParam:
-  return res;
 }
 
 
diff --git a/mps/code/poolmv2.c b/mps/code/poolmv2.c
index 203bf5a8e36..076d39563b4 100644
--- a/mps/code/poolmv2.c
+++ b/mps/code/poolmv2.c
@@ -242,36 +242,23 @@ static Res MVTInit(Pool pool, ArgList args)
   arena = PoolArena(pool);
   AVERT(Arena, arena);
   
-
-  /* FIXME: Inconsistent reporting of bad arguments.  Elsewhere we assert or return ResPARAM. */
-  /* --- Should there be a ResBADARG ? */
-  if (ArgPick(&arg, args, MPS_KEY_MIN_SIZE)) {
+  if (ArgPick(&arg, args, MPS_KEY_MIN_SIZE))
     minSize = arg.val.size;
-    unless (minSize > 0)
-      return ResLIMIT;
-  }
-  if (ArgPick(&arg, args, MPS_KEY_MEAN_SIZE)) {
+  if (ArgPick(&arg, args, MPS_KEY_MEAN_SIZE))
     meanSize = arg.val.size;
-    unless (meanSize >= minSize)
-      return ResLIMIT;
-  }
-  if (ArgPick(&arg, args, MPS_KEY_MAX_SIZE)) {
+  if (ArgPick(&arg, args, MPS_KEY_MAX_SIZE))
     maxSize = arg.val.size;
-    unless (maxSize >= meanSize)
-      return ResLIMIT;
-  }
-  if (ArgPick(&arg, args, MPS_KEY_MVT_RESERVE_DEPTH)) {
-    /* --- check that maxSize is not too large */
+  if (ArgPick(&arg, args, MPS_KEY_MVT_RESERVE_DEPTH))
     reserveDepth = arg.val.count;
-    unless (reserveDepth > 0)
-      return ResLIMIT;
-  }
-  if (ArgPick(&arg, args, MPS_KEY_MVT_FRAG_LIMIT)) {
-    /* --- check that reserveDepth is not too large or small */
+  if (ArgPick(&arg, args, MPS_KEY_MVT_FRAG_LIMIT))
     fragLimit = arg.val.count;
-    unless (fragLimit <= 100)
-      return ResLIMIT;
-  }
+
+  AVER(0 < minSize);
+  AVER(minSize <= meanSize);
+  AVER(meanSize <= maxSize);
+  AVER(reserveDepth > 0);
+  AVER(fragLimit <= 100);
+  /* TODO: More sanity checks possible? */
 
   /* see <design/poolmvt/#arch.parameters> */
   fillSize = SizeAlignUp(maxSize, ArenaAlign(arena));
diff --git a/mps/code/poolsnc.c b/mps/code/poolsnc.c
index 6b01c3a9b02..70c618bf385 100644
--- a/mps/code/poolsnc.c
+++ b/mps/code/poolsnc.c
@@ -363,7 +363,6 @@ static Bool sncFindFreeSeg(Seg *segReturn, SNC snc, Size size)
 
 static Res SNCInit(Pool pool, ArgList args)
 {
-  Res res;
   SNC snc;
   Format format;
   ArgStruct arg;
@@ -373,12 +372,8 @@ static Res SNCInit(Pool pool, ArgList args)
 
   snc = Pool2SNC(pool);
 
-  if (ArgPick(&arg, args, MPS_KEY_FORMAT))
-    format = arg.val.format;
-  else {
-    res = ResPARAM;
-    goto failParam;
-  }
+  ArgRequire(&arg, args, MPS_KEY_FORMAT);
+  format = arg.val.format;
 
   AVERT(Format, format);
   pool->format = format;
@@ -391,9 +386,6 @@ static Res SNCInit(Pool pool, ArgList args)
   AVERT(SNC, snc);
   EVENT2(PoolInitSNC, pool, format);
   return ResOK;
-
-failParam:
-  return res;
 }
 
 
diff --git a/mps/code/segsmss.c b/mps/code/segsmss.c
index 9d69aff302a..02b29504d34 100644
--- a/mps/code/segsmss.c
+++ b/mps/code/segsmss.c
@@ -341,12 +341,8 @@ static Res AMSTInit(Pool pool, ArgList args)
 
   AVERT(Pool, pool);
   
-  if (ArgPick(&arg, args, MPS_KEY_FORMAT))
-    format = arg.val.format;
-  else {
-    res = ResPARAM;
-    goto failParam;
-  }
+  ArgRequire(&arg, args, MPS_KEY_FORMAT);
+  format = arg.val.format;
   
   res = ChainCreate(&chain, pool->arena, 1, &genParam);
   if (res != ResOK)
@@ -369,10 +365,6 @@ static Res AMSTInit(Pool pool, ArgList args)
   amst->sig = AMSTSig;
   AVERT(AMST, amst);
   return ResOK;
-
-failParam:
-  AVER(res != ResOK);
-  return res;
 }