diff --git a/src/core/internal/dassert.d b/src/core/internal/dassert.d
index afb9136a6bb..4aa1371cfc6 100644
--- a/src/core/internal/dassert.d
+++ b/src/core/internal/dassert.d
@@ -95,10 +95,33 @@ private string miniFormat(V)(const scope ref V v)
     }
     else static if (__traits(isIntegral, V))
     {
-        enum printfFormat = getPrintfFormat!V;
-        char[20] val;
-        const len = sprintf(&val[0], printfFormat, v);
-        return val.idup[0 .. len];
+        static if (is(V == char))
+        {
+            // Avoid invalid code points
+            if (v < 0x7F)
+                return ['\'', v, '\''];
+
+            uint tmp = v;
+            return "cast(char) " ~ miniFormat(tmp);
+        }
+        else static if (is(V == wchar) || is(V == dchar))
+        {
+            import core.internal.utf: isValidDchar, toUTF8;
+
+            // Avoid invalid code points
+            if (isValidDchar(v))
+                return toUTF8(['\'', v, '\'']);
+
+            uint tmp = v;
+            return "cast(" ~ V.stringof ~ ") " ~ miniFormat(tmp);
+        }
+        else
+        {
+            enum printfFormat = getPrintfFormat!V;
+            char[20] val;
+            const len = sprintf(&val[0], printfFormat, v);
+            return val.idup[0 .. len];
+        }
     }
     else static if (__traits(isFloating, V))
     {
diff --git a/test/exceptions/src/assert_fail.d b/test/exceptions/src/assert_fail.d
index d7de373b5b4..c4983e51de2 100644
--- a/test/exceptions/src/assert_fail.d
+++ b/test/exceptions/src/assert_fail.d
@@ -63,6 +63,15 @@ void testStrings()
     // https://issues.dlang.org/show_bug.cgi?id=20322
     test("left"w, "right"w, `"left" != "right"`);
     test("left"d, "right"d, `"left" != "right"`);
+
+    test('A', 'B', "'A' != 'B'");
+    test(wchar('❤'), wchar('∑'), "'❤' != '∑'");
+    test(dchar('❤'), dchar('∑'), "'❤' != '∑'");
+
+    // Detect invalid code points
+    test(char(255), 'B', "cast(char) 255 != 'B'");
+    test(wchar(0xD888), wchar('∑'), "cast(wchar) 55432 != '∑'");
+    test(dchar(0xDDDD), dchar('∑'), "cast(dchar) 56797 != '∑'");
 }
 
 void testToString()()