diff --git a/lib/checkbufferoverrun.cpp b/lib/checkbufferoverrun.cpp
index 810232c57..5e2800ac0 100644
--- a/lib/checkbufferoverrun.cpp
+++ b/lib/checkbufferoverrun.cpp
@@ -666,7 +666,7 @@ void CheckBufferOverrun::checkScope(const Token *tok, const std::vector<std::str
         const std::string snprintfPattern = declarationId > 0 ? std::string("snprintf ( %varid% , %num% ,") : ("snprintf ( " + varnames + " , %num% ,");
         if (Token::Match(tok, snprintfPattern.c_str(), declarationId)) {
             const MathLib::bigint n = MathLib::toLongNumber(tok->strAt(4 + varcount));
-            if (n > total_size)
+            if ((n > total_size) && total_size > 0)
                 outOfBoundsError(tok->tokAt(4 + varcount), "snprintf size", true, n, total_size);
         }
 
diff --git a/test/testbufferoverrun.cpp b/test/testbufferoverrun.cpp
index 7709dd15e..d7a4db38a 100644
--- a/test/testbufferoverrun.cpp
+++ b/test/testbufferoverrun.cpp
@@ -3176,6 +3176,17 @@ private:
               "    snprintf(pString, 1024, \"ab\");\n"
               "}");
         ASSERT_EQUALS("", errout.str());
+
+        // #6141 FP: Unknown type is assumed to have size 0
+        check("typedef struct {\n"
+              "    CHAR s[42];\n"
+              "} sct_t;\n"
+              "void foo() {\n"
+              "    sct_t p;\n"
+              "    snprintf(p.s, 42, \"abcdef\");\n"
+              "}\n");
+        ASSERT_EQUALS("", errout.str());
+
     }
 
     void strncat1() {