diff --git a/llvm/utils/extract_symbols.py b/llvm/utils/extract_symbols.py
index 43f603963a205..6f01cd12fcd81 100755
--- a/llvm/utils/extract_symbols.py
+++ b/llvm/utils/extract_symbols.py
@@ -53,7 +53,12 @@ def nm_get_symbols(lib):
     process.stdin.close()
     for line in process.stdout:
         # Look for external symbols that are defined in some section
-        match = re.match("^(\S+)\s+[BDGRSTVW]\s+\S+\s+\S+$", line)
+        # The POSIX format is:
+        #   name   type   value   size
+        # The -P flag displays the size field for symbols only when applicable,
+        # so the last field is optional. There's no space after the value field,
+        # but \s+ match newline also, so \s+\S* will match the optional size field.
+        match = re.match("^(\S+)\s+[BDGRSTVW]\s+\S+\s+\S*$", line)
         if match:
             yield match.group(1)
     process.wait()