diff --git a/src/setup/execute.c b/src/setup/execute.c
index 7a3faa21..f2377f61 100644
--- a/src/setup/execute.c
+++ b/src/setup/execute.c
@@ -130,7 +130,7 @@ execute_context_t *NewExecuteContext(void)
     return result;
 }
 
-void AddCmdLineParameter(execute_context_t *context, char *s, ...)
+void AddCmdLineParameter(execute_context_t *context, const char *s, ...)
 {
     va_list args;
 
diff --git a/src/setup/execute.h b/src/setup/execute.h
index f3e90e3c..21530f14 100644
--- a/src/setup/execute.h
+++ b/src/setup/execute.h
@@ -28,7 +28,7 @@ typedef struct execute_context_s execute_context_t;
 #define IWAD_CHEX     (1 << 5)       /* chex.wad */
 
 execute_context_t *NewExecuteContext(void);
-void AddCmdLineParameter(execute_context_t *context, char *s, ...) PRINTF_ATTR(2, 3);
+void AddCmdLineParameter(execute_context_t *context, const char *s, ...) PRINTF_ATTR(2, 3);
 void PassThroughArguments(execute_context_t *context);
 int ExecuteDoom(execute_context_t *context);
 int FindInstalledIWADs(void);