diff --git a/msvc/ecl-threads.def b/msvc/ecl-threads.def
index de351d234..a03b0e0bd 100755
--- a/msvc/ecl-threads.def
+++ b/msvc/ecl-threads.def
@@ -159,6 +159,7 @@ EXPORTS
 	imod
 	object_to_char
 	object_to_fixnum
+	object_to_unsigned_integer
 	object_to_float
 	object_to_double
 	aref_bv
diff --git a/msvc/ecl.def b/msvc/ecl.def
index 7d8e6aae2..86282cd6f 100644
--- a/msvc/ecl.def
+++ b/msvc/ecl.def
@@ -159,6 +159,7 @@ EXPORTS
 	imod
 	object_to_char
 	object_to_fixnum
+	object_to_unsigned_integer
 	object_to_float
 	object_to_double
 	aref_bv
diff --git a/src/c/cmpaux.d b/src/c/cmpaux.d
index 503037ec6..1033620d9 100644
--- a/src/c/cmpaux.d
+++ b/src/c/cmpaux.d
@@ -86,6 +86,24 @@ object_to_fixnum(cl_object x)
 	}
 }
 
+cl_index
+object_to_unsigned_integer(cl_object x)
+{
+	switch (type_of(x)) {
+	case t_fixnum:
+	case t_bignum:
+		return fixnnint(x);
+	case t_ratio:
+		return (cl_index)number_to_double(x);
+	case t_shortfloat:
+		return (cl_index)sf(x);
+	case t_longfloat:
+		return (cl_index)lf(x);
+	default:
+		FEerror("~S cannot be coerced to a C unsigned int.", 1, x);
+	}
+}
+
 float
 object_to_float(cl_object x)
 {
diff --git a/src/cmp/cmpffi.lsp b/src/cmp/cmpffi.lsp
index fe1471314..b528aee55 100644
--- a/src/cmp/cmpffi.lsp
+++ b/src/cmp/cmpffi.lsp
@@ -134,7 +134,7 @@
 	(wt loc)
 	(return-from wt-coerce-loc))
       (case dest-rep-type
-	((:int :unsigned-int :long :unsigned-long :byte :unsigned-byte :fixnum)
+	((:int :long :byte :fixnum)
 	 (case loc-rep-type
 	   ((:int :unsigned-int :long :unsigned-long :byte :unsigned-byte :fixnum
 		  :float :double)
@@ -145,6 +145,17 @@
 		loc ")"))
 	   (otherwise
 	    (coercion-error))))
+	((:unsigned-int :unsigned-long :unsigned-byte)
+	 (case loc-rep-type
+	   ((:int :unsigned-int :long :unsigned-long :byte :unsigned-byte :fixnum
+		  :float :double)
+	    (wt "((" (rep-type-name dest-rep-type) ")" loc ")"))
+	   ((:object)
+	    (ensure-valid-object-type dest-type)
+	    (wt (if (subtypep (loc-type loc) 'fixnum) "fix(" "object_to_unsigned_integer(")
+		loc ")"))
+	   (otherwise
+	    (coercion-error))))
 	((:char :unsigned-char)
 	 (case loc-rep-type
 	   ((:char :unsigned-char)
@@ -178,8 +189,10 @@
 	    (coercion-error))))
 	((:object)
 	 (case loc-rep-type
-	   ((:int :unsigned-int :long :unsigned-long)
+	   ((:int :long)
 	    (wt "make_integer(" loc ")"))
+	   ((:unsigned-int :unsigned-long)
+	    (wt "make_unsigned_integer(" loc ")"))
 	   ((:byte :unsigned-byte :fixnum)
 	    (wt "MAKE_FIXNUM(" loc ")"))
 	   ((:float)
diff --git a/src/h/external.h b/src/h/external.h
index c22a0c20b..bd88c600e 100644
--- a/src/h/external.h
+++ b/src/h/external.h
@@ -374,6 +374,7 @@ extern cl_fixnum ifloor(cl_fixnum x, cl_fixnum y);
 extern cl_fixnum imod(cl_fixnum x, cl_fixnum y);
 extern char object_to_char(cl_object x);
 extern cl_fixnum object_to_fixnum(cl_object x);
+extern cl_index object_to_unsigned_integer(cl_object x);
 extern float object_to_float(cl_object x);
 extern double object_to_double(cl_object x);
 extern int aref_bv(cl_object x, cl_index index);