diff --git a/fko/fko_common.h b/fko/fko_common.h
index 7963ba77..107a1416 100644
--- a/fko/fko_common.h
+++ b/fko/fko_common.h
@@ -32,7 +32,6 @@
 
 #include <stdio.h>
 #include <sys/types.h>
-#include <ctype.h>
 
 #if STDC_HEADERS
   #include <stdlib.h>
@@ -45,6 +44,13 @@
   #include <unistd.h>
 #endif
 
+#if HAVE_CTYPE_H
+  #include <ctype.h> /* Using this if isdigit() */
+#else
+  /* Fall-back does not account for locale */
+  #define isdigit(c) (c >= 48 && c <= 57)
+#endif
+
 /* Convenient macros for wrapping sections in 'extern "C" {' constructs.
 */
 #ifdef __cplusplus
diff --git a/fko/fko_message.c b/fko/fko_message.c
index 2cc79e0c..a53ffdf1 100644
--- a/fko/fko_message.c
+++ b/fko/fko_message.c
@@ -202,8 +202,11 @@ int validate_access_msg(const char *msg)
     */
     ndx++;
     while(*ndx != '\0')
-        if(isdigit(*(ndx++)) == 0)
+    {
+        if(isdigit(*ndx) == 0)
             return(FKO_ERROR_INVALID_SPA_ACCESS_MSG);
+        ndx++;
+    }
 
     return(FKO_SUCCESS);
 }