diff --git a/wsutil/to_str.c b/wsutil/to_str.c
index ec6b01aa82..f30ad0bcb7 100644
--- a/wsutil/to_str.c
+++ b/wsutil/to_str.c
@@ -179,7 +179,7 @@ bytes_to_hexstr(char *out, const guint8 *ad, size_t len)
 {
 	size_t i;
 
-	ws_return_ptr_if_null(ad, NULL);
+	ws_return_val_if_null(ad, NULL);
 
 	for (i = 0; i < len; i++)
 		out = byte_to_hex(out, ad[i]);
@@ -199,7 +199,7 @@ bytes_to_hexstr_punct(char *out, const guint8 *ad, size_t len, char punct)
 {
 	size_t i;
 
-	ws_return_ptr_if_null(ad, NULL);
+	ws_return_val_if_null(ad, NULL);
 
 	out = byte_to_hex(out, ad[0]);
 	for (i = 1; i < len; i++) {
diff --git a/wsutil/ws_return.h b/wsutil/ws_return.h
index 6f4034b6f1..454e44936e 100644
--- a/wsutil/ws_return.h
+++ b/wsutil/ws_return.h
@@ -12,33 +12,50 @@
 #include <wsutil/wslog.h>
 #include <wsutil/wmem/wmem.h>
 
-#define ws_warn_zero_len() ws_warning("Zero length passed to %s", __func__)
+/*
+ * These macros can be used as an alternative to ws_assert() to
+ * assert some condition on function arguments. This must only be used
+ * to catch programming errors, in situations where an assertion is
+ * appropriate. And it should only be used if failing the condition
+ * doesn't necessarily lead to an inconsistent state for the program.
+ *
+ * It is possible to set the fatal log level to "critical" to abort
+ * execution for debugging purposes, if one of these checks fail.
+ */
 
-#define ws_warn_null_ptr() ws_warning("Null pointer passed to %s", __func__)
+#define ws_warn_zero_len(var) ws_critical("Zero length '%s' passed to %s()", var, __func__)
+
+#define ws_warn_null_ptr(var) ws_critical("Null pointer '%s' passed to %s()", var, __func__)
 
 
 #define ws_return_str_if_zero(scope, len) \
         do { \
             if (!(len)) { \
-                ws_warn_zero_len(); \
+                ws_warn_zero_len(#len); \
                 return wmem_strdup(scope, "(zero length)"); \
             } \
         } while (0)
 
-
 #define ws_return_str_if_null(scope, ptr) \
         do { \
             if (!(ptr)) { \
-                ws_warn_null_ptr(); \
+                ws_warn_null_ptr(#ptr); \
                 return wmem_strdup(scope, "(null pointer)"); \
             } \
         } while (0)
 
+#define ws_return_val_if_zero(len, val) \
+        do { \
+            if (!(len)) { \
+                ws_warn_zero_len(#len); \
+                return (val); \
+            } \
+        } while (0)
 
-#define ws_return_ptr_if_null(ptr, val) \
+#define ws_return_val_if_null(ptr, val) \
         do { \
             if (!(ptr)) { \
-                ws_warn_null_ptr(); \
+                ws_warn_null_ptr(#ptr); \
                 return (val); \
             } \
         } while (0)