diff --git a/deps/v8/include/v8-version.h b/deps/v8/include/v8-version.h
index 0fcab08efa4b10..113e02667508ad 100644
--- a/deps/v8/include/v8-version.h
+++ b/deps/v8/include/v8-version.h
@@ -11,7 +11,7 @@
 #define V8_MAJOR_VERSION 6
 #define V8_MINOR_VERSION 2
 #define V8_BUILD_NUMBER 414
-#define V8_PATCH_LEVEL 65
+#define V8_PATCH_LEVEL 66
 
 // Use 1 for candidates and 0 otherwise.
 // (Boolean macro values are not supported by all preprocessors.)
diff --git a/deps/v8/src/compiler/s390/instruction-selector-s390.cc b/deps/v8/src/compiler/s390/instruction-selector-s390.cc
index 3ed0a34c720da6..793ec86b53cd9e 100644
--- a/deps/v8/src/compiler/s390/instruction-selector-s390.cc
+++ b/deps/v8/src/compiler/s390/instruction-selector-s390.cc
@@ -318,12 +318,12 @@ ArchOpcode SelectLoadOpcode(Node* node) {
   /* Float unary op*/              \
   V(BitcastFloat32ToInt32)         \
   /* V(TruncateFloat64ToWord32) */ \
-  /* V(RoundFloat64ToInt32)     */ \
-  /* V(TruncateFloat32ToInt32)  */ \
-  /* V(TruncateFloat32ToUint32) */ \
-  /* V(TruncateFloat64ToUint32) */ \
-  /* V(ChangeFloat64ToInt32)    */ \
-  /* V(ChangeFloat64ToUint32)   */ \
+  V(RoundFloat64ToInt32)           \
+  V(TruncateFloat32ToInt32)        \
+  V(TruncateFloat32ToUint32)       \
+  V(TruncateFloat64ToUint32)       \
+  V(ChangeFloat64ToInt32)          \
+  V(ChangeFloat64ToUint32)         \
   /* Word32 unary op */            \
   V(Word32Clz)                     \
   V(Word32Popcnt)                  \
diff --git a/deps/v8/src/s390/macro-assembler-s390.cc b/deps/v8/src/s390/macro-assembler-s390.cc
index 931233b2d587bf..45331a6b991260 100644
--- a/deps/v8/src/s390/macro-assembler-s390.cc
+++ b/deps/v8/src/s390/macro-assembler-s390.cc
@@ -704,6 +704,9 @@ void TurboAssembler::ConvertDoubleToInt32(const Register dst,
       UNIMPLEMENTED();
       break;
   }
+#ifdef V8_TARGET_ARCH_S390X
+  lghi(dst, Operand::Zero());
+#endif
   cfdbr(m, dst, double_input);
 }
 
@@ -728,6 +731,9 @@ void TurboAssembler::ConvertFloat32ToInt32(const Register result,
       UNIMPLEMENTED();
       break;
   }
+#ifdef V8_TARGET_ARCH_S390X
+  lghi(result, Operand::Zero());
+#endif
   cfebr(m, result, double_input);
 }
 
@@ -752,6 +758,9 @@ void TurboAssembler::ConvertFloat32ToUnsignedInt32(
       UNIMPLEMENTED();
       break;
   }
+#ifdef V8_TARGET_ARCH_S390X
+  lghi(result, Operand::Zero());
+#endif
   clfebr(m, Condition(0), result, double_input);
 }
 
@@ -824,6 +833,9 @@ void TurboAssembler::ConvertDoubleToUnsignedInt32(
       UNIMPLEMENTED();
       break;
   }
+#ifdef V8_TARGET_ARCH_S390X
+  lghi(dst, Operand::Zero());
+#endif
   clfdbr(m, Condition(0), dst, double_input);
 }