diff --git a/src/tools/moc/preprocessor.cpp b/src/tools/moc/preprocessor.cpp
index e51a0059354..eb8eaea2155 100644
--- a/src/tools/moc/preprocessor.cpp
+++ b/src/tools/moc/preprocessor.cpp
@@ -223,7 +223,8 @@ Symbols Preprocessor::tokenize(const QByteArray& input, int lineNum, Preprocesso
                             ++data;
                             while (is_hex_char(*data) || *data == '\'')
                                 ++data;
-                        }
+                        } else if (*data == 'L') // TODO: handle other suffixes
+                            ++data;
                         break;
                     }
                     token = FLOATING_LITERAL;
@@ -400,7 +401,8 @@ Symbols Preprocessor::tokenize(const QByteArray& input, int lineNum, Preprocesso
                         ++data;
                         while (is_hex_char(*data) || *data == '\'')
                             ++data;
-                    }
+                    } else if (*data == 'L') // TODO: handle other suffixes
+                        ++data;
                     break;
                 }
                 token = PP_FLOATING_LITERAL;
@@ -930,7 +932,11 @@ int PP_Expression::primary_expression()
         test(PP_RPAREN);
     } else {
         next();
-        value = lexem().toInt(nullptr, 0);
+        const QByteArray &lex = lexem();
+        auto lexView = QByteArrayView(lex);
+        if (lex.endsWith('L'))
+            lexView.chop(1);
+        value = lexView.toInt(nullptr, 0);
     }
     return value;
 }
diff --git a/tests/auto/tools/moc/tst_moc.cpp b/tests/auto/tools/moc/tst_moc.cpp
index a509c0ddae0..77316aa43ea 100644
--- a/tests/auto/tools/moc/tst_moc.cpp
+++ b/tests/auto/tools/moc/tst_moc.cpp
@@ -617,6 +617,10 @@ private slots:
 
 QT_WARNING_POP
 
+// quick test to verify that moc handles the L suffix
+// correctly in the preprocessor
+#if 2000L < 1
+#else
 class PropertyTestClass : public QObject
 {
     Q_OBJECT
@@ -626,6 +630,7 @@ public:
 
     Q_ENUM(TestEnum)
 };
+#endif
 
 class PropertyUseClass : public QObject
 {