diff --git a/tool/abi_symbols b/tool/abi_symbols
index 16e64f53f..1a0eace76 100755
--- a/tool/abi_symbols
+++ b/tool/abi_symbols
@@ -37,10 +37,14 @@ foreach line [split $symbols "\n"] {
 	set type "U"
 
 	# match undefined symbol
-	regexp {^(\w+) U\s*$} $line dummy name
+	if {![regexp {^(\w+) U\s*$} $line dummy name]} {
 
-	# match defined symbol, which does not always feature a size value
-	regexp {^([\w.]+) (\w) \w+ ?(\w*)$} $line dummy name type size_hex
+		# match defined symbol, which does not always feature a size value
+		if {![regexp {^([\w.]+) (\w) \w+ ?(\w*)$} $line dummy name type size_hex]} {
+			puts stderr "Error: unexpected format of line: $line"
+			exit -1
+		}
+	}
 
 	# decimal symbol size
 	set size_dec [expr 0x0$size_hex]