diff --git a/src/include/deepstate/DeepState.h b/src/include/deepstate/DeepState.h
index 6838ac4..834d5bb 100644
--- a/src/include/deepstate/DeepState.h
+++ b/src/include/deepstate/DeepState.h
@@ -165,8 +165,7 @@ extern void *DeepState_ConcretizeData(void *begin, void *end);
 
 /* Assign a symbolic C string of length `len` with only chars in allowed,
  * if allowed is non-null */
-extern void DeepState_AssignCStr(char* str, size_t len, const char* allowed,
-				 size_t allowed_size);
+extern void DeepState_AssignCStr(char* str, size_t len, const char* allowed);
 
 /* Return a symbolic C string of length `len`. */
 extern char *DeepState_CStr(size_t len);
diff --git a/src/include/deepstate/DeepState.hpp b/src/include/deepstate/DeepState.hpp
index d9f148d..cb27062 100644
--- a/src/include/deepstate/DeepState.hpp
+++ b/src/include/deepstate/DeepState.hpp
@@ -472,10 +472,10 @@ struct Comparer {
 };
 
 /* Like DeepState_AssignCStr, but Pumps through possible string sizes. */
-inline static void DeepState_AssignCStrMax(char* str, size_t max_len, const char* allowed,
-					   size_t allowed_size) {
+inline static void DeepState_AssignCStrMax(char* str, size_t max_len,
+					   const char* allowed) {
   uint32_t size = DeepState_UIntInRange(0, max_len);
-  DeepState_AssignCStr(str, Pump(size, max_len), allowed, allowed_size);  
+  DeepState_AssignCStr(str, Pump(size, max_len), allowed);  
 }
 
 /* Like DeepState_CStr, but Pumps through possible string sizes. */
diff --git a/src/lib/DeepState.c b/src/lib/DeepState.c
index 6f2860a..5d81f2b 100644
--- a/src/lib/DeepState.c
+++ b/src/lib/DeepState.c
@@ -176,14 +176,14 @@ void *DeepState_ConcretizeData(void *begin, void *end) {
 }
 
 /* Assign a symbolic C string of length `len`. */
-void DeepState_AssignCStr(char* str, size_t len, const char* allowed,
-			   size_t allowed_size) {
+void DeepState_AssignCStr(char* str, size_t len, const char* allowed) {
   if (SIZE_MAX == len) {
     DeepState_Abandon("Can't create an SIZE_MAX-length string.");
   }
   if (NULL == str) {
     DeepState_Abandon("Attempted to populate null pointer.");
   }
+  uint32_t allowed_size = strlen(allowed);
   for (int i = 0; i < len; i++) {
     str[i] = allowed[DeepState_UIntInRange(0, allowed_size)];
   }