Index: src/invocation/invoke-x86_64.m
==================================================================
--- src/invocation/invoke-x86_64.m
+++ src/invocation/invoke-x86_64.m
@@ -149,10 +149,20 @@
 		CASE_GPR('S', unsigned short)
 		CASE_GPR('l', long)
 		CASE_GPR('L', unsigned long)
 		CASE_GPR('q', long long)
 		CASE_GPR('Q', unsigned long long)
+#ifdef __SIZEOF_INT128__
+		case 't':
+		case 'T':;
+			uint64_t int128Tmp[2];
+			[invocation getArgument: int128Tmp
+					atIndex: i];
+			pushGPR(&context, &currentGPR, int128Tmp[0]);
+			pushGPR(&context, &currentGPR, int128Tmp[1]);
+			break;
+#endif
 		case 'f':;
 			float floatTmp;
 			[invocation getArgument: &floatTmp
 					atIndex: i];
 			pushDouble(&context, &currentSSE, floatTmp);
@@ -179,14 +189,10 @@
 		/* TODO: '(' */
 		CASE_GPR('^', uintptr_t)
 #ifndef __STDC_NO_COMPLEX__
 		/* TODO: 'j' */
 #endif
-#ifdef __SIZEOF_INT128__
-		/* TODO: 't' */
-		/* TODO: 'T' */
-#endif
 		default:
 			free(context);
 			@throw [OFInvalidFormatException exception];
 #undef CASE_GPR
 		}
@@ -206,10 +212,14 @@
 	case 'S':
 	case 'l':
 	case 'L':
 	case 'q':
 	case 'Q':
+#ifdef __SIZEOF_INT128__
+	case 't':
+	case 'T':
+#endif
 	case 'f':
 	case 'd':
 	case 'B':
 	case '*':
 	case '@':
@@ -225,14 +235,10 @@
 	/* TODO: '{' */
 	/* TODO: '(' */
 #ifndef __STDC_NO_COMPLEX__
 	/* TODO: 'j' */
 #endif
-#ifdef __SIZEOF_INT128__
-	/* TODO: 't' */
-	/* TODO: 'T' */
-#endif
 	default:
 		free(context);
 		@throw [OFInvalidFormatException exception];
 	}
 
@@ -254,10 +260,16 @@
 		CASE_GPR('S', unsigned short)
 		CASE_GPR('l', long)
 		CASE_GPR('L', unsigned long)
 		CASE_GPR('q', long long)
 		CASE_GPR('Q', unsigned long long)
+#ifdef __SIZEOF_INT128__
+		case 't':
+		case 'T':;
+			[invocation setReturnValue: &context->gpr[NUM_GPR_IN]];
+			break;
+#endif
 		case 'f':;
 			float floatTmp;
 			_mm_store_ss(&floatTmp, context->sse[0]);
 			[invocation setReturnValue: &floatTmp];
 			break;
@@ -279,17 +291,13 @@
 		/* TODO: '(' */
 		CASE_GPR('^', uintptr_t)
 #ifndef __STDC_NO_COMPLEX__
 		/* TODO: 'j' */
 #endif
-#ifdef __SIZEOF_INT128__
-		/* TODO: 't' */
-		/* TODO: 'T' */
-#endif
 		default:
 			free(context);
 			@throw [OFInvalidFormatException exception];
 #undef CASE_GPR
 	}
 
 	free(context);
 }

Index: tests/OFInvocationTests.m
==================================================================
--- tests/OFInvocationTests.m
+++ tests/OFInvocationTests.m
@@ -100,10 +100,53 @@
 				    : (long double)d16
 {
 	return (d1 + d2 + d3 + d4 + d5 + d6 + d7 + d8 + d9 + d10 + d11 +
 	    d12 + d13 + d14 + d15 + d16) / 16;
 }
+
+#ifdef __SIZEOF_INT128__
+- (__int128)invocationTestMethod5: (__int128)i1
+				 : (__int128)i2
+				 : (int)i3	 /* to check alignment */
+				 : (__int128)i4
+				 : (__int128)i5
+				 : (__int128)i6
+				 : (__int128)i7
+				 : (__int128)i8
+				 : (__int128)i9
+				 : (__int128)i10
+				 : (__int128)i11
+				 : (__int128)i12
+				 : (__int128)i13
+				 : (__int128)i14
+				 : (__int128)i15
+				 : (__int128)i16
+{
+	__int128 mask = (__int128)0xFFFFFFFFFFFFFFFF << 64;
+
+	OF_ENSURE(i1 == mask + 1);
+	OF_ENSURE(i2 == mask + 2);
+	OF_ENSURE(i3 == 3);
+	OF_ENSURE(i4 == mask + 4);
+	OF_ENSURE(i5 == mask + 5);
+	OF_ENSURE(i6 == mask + 6);
+	OF_ENSURE(i7 == mask + 7);
+	OF_ENSURE(i8 == mask + 8);
+	OF_ENSURE(i9 == mask + 9);
+	OF_ENSURE(i10 == mask + 10);
+	OF_ENSURE(i11 == mask + 11);
+	OF_ENSURE(i12 == mask + 12);
+	OF_ENSURE(i13 == mask + 13);
+	OF_ENSURE(i14 == mask + 14);
+	OF_ENSURE(i15 == mask + 15);
+	OF_ENSURE(i16 == mask + 16);
+
+	return (((int)i1 + (int)i2 + (int)i3 + (int)i4 + (int)i5 + (int)i6 +
+	    (int)i7 + (int)i8 + (int)i9 + (int)i10 + (int)i11 + (int)i12 +
+	    (int)i13 + (int)i14 + (int)i15 + (int)i16) / 16) + mask;
+}
+#endif
 
 - (void)invocationTests
 {
 	OFAutoreleasePool *pool = [[OFAutoreleasePool alloc] init];
 	SEL selector = @selector(invocationTestMethod1::::);
@@ -218,10 +261,40 @@
 		long double longDoubleResult;
 		TEST(@"-[invoke] #3", R([invocation invoke]) &&
 		    R([invocation getReturnValue: &longDoubleResult]) &&
 		    longDoubleResult == 8.5)
 	}
+
+# ifdef __SIZEOF_INT128__
+	/* -[invoke] #4 */
+	selector = @selector(invocationTestMethod5::::::::::::::::);
+	invocation = [OFInvocation invocationWithMethodSignature:
+	    [self methodSignatureForSelector: selector]];
+
+	[invocation setArgument: &self
+			atIndex: 0];
+	[invocation setArgument: &selector
+			atIndex: 1];
+
+	for (int i = 1; i <= 16; i++) {
+		__int128 i128 = 0xFFFFFFFFFFFFFFFF;
+		i128 <<= 64;
+		i128 |= i;
+
+		if (i == 3)
+			[invocation setArgument: &i
+					atIndex: i + 1];
+		else
+			[invocation setArgument: &i128
+					atIndex: i + 1];
+	}
+
+	__int128 int128Result;
+	TEST(@"-[invoke] #4", R([invocation invoke]) &&
+	    R([invocation getReturnValue: &int128Result]) &&
+	    int128Result == ((__int128)0xFFFFFFFFFFFFFFFF << 64) + 8)
+# endif
 #endif
 
 	[pool drain];
 }
 @end