diff --git a/include/asm/charmap.hpp b/include/asm/charmap.hpp
index 5f72ff40..b92e36a2 100644
--- a/include/asm/charmap.hpp
+++ b/include/asm/charmap.hpp
@@ -12,7 +12,7 @@ void charmap_New(char const *name, char const *baseName);
 void charmap_Set(char const *name);
 void charmap_Push();
 void charmap_Pop();
-void charmap_Add(char *mapping, uint8_t value);
+void charmap_Add(char const *mapping, uint8_t value);
 bool charmap_HasChar(char const *input);
 void charmap_Convert(char const *input, std::vector<uint8_t> &output);
 size_t charmap_ConvertNext(char const *&input, std::vector<uint8_t> *output);
diff --git a/include/asm/opt.hpp b/include/asm/opt.hpp
index 03f05456..8ea6069c 100644
--- a/include/asm/opt.hpp
+++ b/include/asm/opt.hpp
@@ -10,8 +10,8 @@ void opt_G(char const chars[4]);
 void opt_P(uint8_t padByte);
 void opt_Q(uint8_t precision);
 void opt_L(bool optimize);
-void opt_W(char *flag);
-void opt_Parse(char *option);
+void opt_W(char const *flag);
+void opt_Parse(char const *option);
 
 void opt_Push();
 void opt_Pop();
diff --git a/include/asm/warning.hpp b/include/asm/warning.hpp
index a7e3b008..be2613d9 100644
--- a/include/asm/warning.hpp
+++ b/include/asm/warning.hpp
@@ -57,7 +57,7 @@ enum WarningID {
 extern enum WarningState warningStates[NB_PLAIN_AND_PARAM_WARNINGS];
 extern bool warningsAreErrors;
 
-void processWarningFlag(char *flag);
+void processWarningFlag(char const *flag);
 
 /*
  * Used to warn the user about problems that don't prevent the generation of
diff --git a/src/asm/charmap.cpp b/src/asm/charmap.cpp
index 7a626acc..ae9d0b66 100644
--- a/src/asm/charmap.cpp
+++ b/src/asm/charmap.cpp
@@ -91,7 +91,7 @@ void charmap_Pop() {
 	charmapStack.pop();
 }
 
-void charmap_Add(char *mapping, uint8_t value) {
+void charmap_Add(char const *mapping, uint8_t value) {
 	Charmap &charmap = *currentCharmap;
 	size_t nodeIdx = 0;
 
diff --git a/src/asm/opt.cpp b/src/asm/opt.cpp
index abcbb290..145c2ac1 100644
--- a/src/asm/opt.cpp
+++ b/src/asm/opt.cpp
@@ -70,11 +70,11 @@ void opt_l(bool warn) {
 	warnOnLdOpt = warn;
 }
 
-void opt_W(char *flag) {
+void opt_W(char const *flag) {
 	processWarningFlag(flag);
 }
 
-void opt_Parse(char *s) {
+void opt_Parse(char const *s) {
 	switch (s[0]) {
 	case 'b':
 		if (strlen(&s[1]) == 2)
diff --git a/src/asm/warning.cpp b/src/asm/warning.cpp
index bc49ec69..06644839 100644
--- a/src/asm/warning.cpp
+++ b/src/asm/warning.cpp
@@ -210,7 +210,7 @@ static uint8_t const *metaWarningCommands[NB_META_WARNINGS] = {
     _weverythingCommands,
 };
 
-void processWarningFlag(char *flag) {
+void processWarningFlag(char const *flag) {
 	static bool setError = false;
 
 	// First, try to match against a "meta" warning
@@ -235,7 +235,7 @@ void processWarningFlag(char *flag) {
 
 	// If it's not a meta warning, specially check against `-Werror`
 	if (!strncmp(flag, "error", strlen("error"))) {
-		char *errorFlag = flag + strlen("error");
+		char const *errorFlag = flag + strlen("error");
 
 		switch (*errorFlag) {
 		case '\0':
@@ -260,12 +260,12 @@ void processWarningFlag(char *flag) {
 	                          // Not an error, then check if this is a negation
 	                          : strncmp(flag, "no-", strlen("no-")) ? WARNING_ENABLED
 	                                                                : WARNING_DISABLED;
-	char *rootFlag = state == WARNING_DISABLED ? flag + strlen("no-") : flag;
+	char const *rootFlag = state == WARNING_DISABLED ? flag + strlen("no-") : flag;
 
 	// Is this a "parametric" warning?
 	if (state != WARNING_DISABLED) { // The `no-` form cannot be parametrized
 		// First, check if there is an "equals" sign followed by a decimal number
-		char *equals = strchr(rootFlag, '=');
+		char const *equals = strchr(rootFlag, '=');
 
 		if (equals && equals[1] != '\0') { // Ignore an equal sign at the very end as well
 			// Is the rest of the string a decimal number?
@@ -299,8 +299,13 @@ void processWarningFlag(char *flag) {
 					warnx("Ignoring nonsensical warning flag \"%s\"\n", flag);
 					return;
 				}
-				*equals = '\0'; // Truncate the param at the '='
-				if (tryProcessParamWarning(rootFlag, param, param == 0 ? WARNING_DISABLED : state))
+
+				std::string truncFlag = rootFlag;
+
+				truncFlag.resize(equals - rootFlag); // Truncate the param at the '='
+				if (tryProcessParamWarning(
+				        truncFlag.c_str(), param, param == 0 ? WARNING_DISABLED : state
+				    ))
 					return;
 			}
 		}