diff --git a/src/asm/charmap.cpp b/src/asm/charmap.cpp
index 50c573f4..aae73a74 100644
--- a/src/asm/charmap.cpp
+++ b/src/asm/charmap.cpp
@@ -105,6 +105,11 @@ void charmap_Pop() {
 }
 
 void charmap_Add(std::string const &mapping, std::vector<int32_t> &&value) {
+	if (mapping.empty()) {
+		error("Cannot map an empty string\n");
+		return;
+	}
+
 	Charmap &charmap = *currentCharmap;
 	size_t nodeIdx = 0;
 
diff --git a/test/asm/charmap-empty.asm b/test/asm/charmap-empty.asm
new file mode 100644
index 00000000..5a496994
--- /dev/null
+++ b/test/asm/charmap-empty.asm
@@ -0,0 +1,2 @@
+charmap "", 1
+charmap "nonempty", ; nothing
diff --git a/test/asm/charmap-empty.err b/test/asm/charmap-empty.err
new file mode 100644
index 00000000..fcef645f
--- /dev/null
+++ b/test/asm/charmap-empty.err
@@ -0,0 +1,5 @@
+error: charmap-empty.asm(1):
+    Cannot map an empty string
+error: charmap-empty.asm(2):
+    syntax error, unexpected newline
+error: Assembly aborted (2 errors)!