diff --git a/core/src/strutil.c b/core/src/strutil.c
index ffc698b..c02490f 100644
--- a/core/src/strutil.c
+++ b/core/src/strutil.c
@@ -16,7 +16,7 @@ uintptr_t strhash(const char* s) {
 
 long strlast(const char* rbegin, const char* rend, char search) {
     const char* itr = rbegin;
-    while(itr != rend)
+    while(itr < rend && *itr != '\0')
         if(*itr == search) return itr - rend;
         else itr--;
     return -1;
@@ -24,7 +24,7 @@ long strlast(const char* rbegin, const char* rend, char search) {
 
 long strfirst(const char* begin, const char* end, char search) {
     const char* itr = begin;
-    while(itr != end)
+    while(itr < end && *itr != '\0')
         if(*itr == search) return itr - begin;
         else itr++;
     return -1;
@@ -39,7 +39,7 @@ long strcount(const char* begin, const char* end, char search) {
 
 long strfirst_pred(const char* begin, const char* end, CharPredFn pred) {
     const char* itr = begin;
-    while(itr != end)
+    while(itr < end && *itr != '\0')
         if(pred(*itr)) return itr - begin;
         else itr++;
     return -1;
@@ -47,7 +47,7 @@ long strfirst_pred(const char* begin, const char* end, CharPredFn pred) {
 
 long strlast_pred(const char* rbegin, const char* rend, CharPredFn pred) {
     const char* itr = rbegin;
-    while(itr != rend)
+    while(itr < rend && *itr != '\0')
         if(pred(*itr)) return itr - rend;
         else itr--;
     return -1;