diff --git a/libs/main/core/pistring.cpp b/libs/main/core/pistring.cpp
index 781f3cc2..b3338317 100644
--- a/libs/main/core/pistring.cpp
+++ b/libs/main/core/pistring.cpp
@@ -235,7 +235,7 @@ void PIString::appendFromChars(const char * c, int s, const char * codepage) {
 	memset(&state, 0, sizeof(state));
 	const char ** pc;
 	if (s > 0) {
-		char c_ [s+1];
+		const char c_ [s+1];
 		memcpy(c_, c, s);
 		c_[s] = '\0';
 		pc = &c_;