diff --git a/src/c/unixsys.d b/src/c/unixsys.d
index 1179cc32a..5ed56f470 100644
--- a/src/c/unixsys.d
+++ b/src/c/unixsys.d
@@ -310,7 +310,7 @@ create_descriptor(cl_object stream, cl_object direction,
                     DUPLICATE_SAME_ACCESS);
   }
   else {
-    FEerror("Invalid ~S argument to EXT:RUN-PROGRAM", 1, stream);
+    FEerror("Invalid ~S argument to EXT:RUN-PROGRAM.", 1, stream);
   }
 }
 #else
@@ -345,7 +345,7 @@ create_descriptor(cl_object stream, cl_object direction,
     }
   }
   else {
-    FEerror("Invalid ~S argument to EXT:RUN-PROGRAM", 1, stream);
+    FEerror("Invalid ~S argument to EXT:RUN-PROGRAM.", 1, stream);
   }
 }
 #endif