diff --git a/sim_defs.h b/sim_defs.h
index b98ae56c..507446e4 100644
--- a/sim_defs.h
+++ b/sim_defs.h
@@ -108,6 +108,9 @@
 #include <stddef.h>
 #include <stdlib.h>
 #include <stdio.h>
+#if defined(_MSC_VER) && (_MSC_VER < 1900)
+#define snprintf _snprintf      /* poor man's snprintf which will work most of the time but has different return value */
+#endif
 #include <stdarg.h>
 #include <string.h>
 #include <errno.h>
@@ -844,11 +847,9 @@ typedef struct sim_bitfield BITFIELD;
 /* This replaces any references to "assert()" which should never be invoked */
 /* with an expression which causes side effects (i.e. must be executed for */
 /* the program to work correctly) */
-#define ASSURE(_Expression) if (!(_Expression)) {const char *_exp = #_Expression; const char *_file = __FILE__;                                 \
-                                                 fprintf(stderr, "%s failed at %s line %d\n", _exp, _file, __LINE__);               \
-                                                 if (sim_log) fprintf(sim_log, "%s failed at %s line %d\n", _exp, _file, __LINE__); \
-                                                 if (sim_deb) fprintf(sim_deb, "%s failed at %s line %d\n", _exp, _file, __LINE__); \
-                                                 abort();} else (void)0
+#define ASSURE(_Expression) while (!(_Expression)) {fprintf(stderr, "%s failed at %s line %d\n", #_Expression, __FILE__, __LINE__);  \
+                                                    sim_printf("%s failed at %s line %d\n", #_Expression, __FILE__, __LINE__);       \
+                                                    abort();}
 
 /* Asynch/Threaded I/O support */