1 files changed, 1 insertions, 1 deletions
diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index 8bc60ec2d..c0b9698ee 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -1450,7 +1450,7 @@ string base64Decode(std::string_view s)
 
         char digit = decode[(unsigned char) c];
         if (digit == -1)
-            throw Error("invalid character in Base64 string");
+            throw Error("invalid character in Base64 string: '%c'", c);
 
         bits += 6;
         d = d << 6 | digit;