diff --git a/lib/addon.cc b/lib/addon.cc
index 0dc7f73..37c8bbf 100644
--- a/lib/addon.cc
+++ b/lib/addon.cc
@@ -119,6 +119,8 @@ const StrVal &WrappedRE2::prepareArgument(const v8::Local<v8::Value> &arg, bool
 	if (lastString == arg && !node::Buffer::HasInstance(arg) && !lastCache.IsEmpty())
 	{
 		// we have a properly cached string
+		lastString.ClearWeak();
+		lastCache.ClearWeak();
 		lastStringValue.setIndex(startFrom);
 		return lastStringValue;
 	}
@@ -130,7 +132,6 @@ const StrVal &WrappedRE2::prepareArgument(const v8::Local<v8::Value> &arg, bool
 		// no need to cache buffers
 
 		lastString.Reset(arg);
-		static_cast<v8::PersistentBase<v8::Value> &>(lastString).SetWeak();
 
 		auto argSize = node::Buffer::Length(arg);
 		lastStringValue.reset(arg, argSize, argSize, startFrom, true);
@@ -149,14 +150,12 @@ const StrVal &WrappedRE2::prepareArgument(const v8::Local<v8::Value> &arg, bool
 	}
 
 	lastString.Reset(arg);
-	static_cast<v8::PersistentBase<v8::Value> &>(lastString).SetWeak();
 
 	auto s = t.ToLocalChecked();
 	auto argLength = Nan::DecodeBytes(s);
 
 	auto buffer = node::Buffer::New(v8::Isolate::GetCurrent(), s).ToLocalChecked();
 	lastCache.Reset(buffer);
-	static_cast<v8::PersistentBase<v8::Object> &>(lastCache).SetWeak();
 
 	auto argSize = node::Buffer::Length(buffer);
 	lastStringValue.reset(buffer, argSize, argLength, startFrom);
@@ -164,6 +163,19 @@ const StrVal &WrappedRE2::prepareArgument(const v8::Local<v8::Value> &arg, bool
 	return lastStringValue;
 };
 
+void WrappedRE2::doneWithLastString()
+{
+	if (!lastString.IsEmpty())
+	{
+		static_cast<v8::PersistentBase<v8::Value> &>(lastString).SetWeak();
+	}
+
+	if (!lastCache.IsEmpty())
+	{
+		static_cast<v8::PersistentBase<v8::Object> &>(lastCache).SetWeak();
+	}
+}
+
 // StrVal
 
 void StrVal::setIndex(size_t newIndex)
diff --git a/lib/exec.cc b/lib/exec.cc
index 29729f8..7d016ae 100644
--- a/lib/exec.cc
+++ b/lib/exec.cc
@@ -14,7 +14,8 @@ NAN_METHOD(WrappedRE2::Exec)
 		return;
 	}
 
-	auto str = re2->prepareArgument(info[0]);
+	PrepareLastString prep(re2, info[0]);
+	StrVal& str = prep;
 	if (str.isBad) return; // throws an exception
 
 	if (re2->global || re2->sticky)
diff --git a/lib/match.cc b/lib/match.cc
index 59176dc..d92c2d7 100644
--- a/lib/match.cc
+++ b/lib/match.cc
@@ -14,7 +14,8 @@ NAN_METHOD(WrappedRE2::Match)
 		return;
 	}
 
-	auto str = re2->prepareArgument(info[0], re2->global);
+	PrepareLastString prep(re2, info[0]);
+	StrVal& str = prep;
 	if (str.isBad) return; // throws an exception
 
 	if (!str.isValidIndex)
diff --git a/lib/replace.cc b/lib/replace.cc
index cee3185..2528989 100644
--- a/lib/replace.cc
+++ b/lib/replace.cc
@@ -497,7 +497,8 @@ NAN_METHOD(WrappedRE2::Replace)
 		return;
 	}
 
-	auto replacee = re2->prepareArgument(info[0]);
+	PrepareLastString prep(re2, info[0]);
+	StrVal& replacee = prep;
 	if (replacee.isBad) return; // throws an exception
 
 	if (!replacee.isValidIndex)
diff --git a/lib/search.cc b/lib/search.cc
index 1d02761..6846ac6 100644
--- a/lib/search.cc
+++ b/lib/search.cc
@@ -12,7 +12,8 @@ NAN_METHOD(WrappedRE2::Search)
 		return;
 	}
 
-	auto str = re2->prepareArgument(info[0], true);
+	PrepareLastString prep(re2, info[0]);
+	StrVal& str = prep;
 	if (str.isBad) return; // throws an exception
 
 	if (!str.data)
diff --git a/lib/split.cc b/lib/split.cc
index ceaa545..26b595b 100644
--- a/lib/split.cc
+++ b/lib/split.cc
@@ -19,7 +19,8 @@ NAN_METHOD(WrappedRE2::Split)
 		return;
 	}
 
-	auto str = re2->prepareArgument(info[0], true);
+	PrepareLastString prep(re2, info[0]);
+	StrVal& str = prep;
 	if (str.isBad) return; // throws an exception
 
 	size_t limit = std::numeric_limits<size_t>::max();
diff --git a/lib/test.cc b/lib/test.cc
index 8abf584..76c6a6f 100644
--- a/lib/test.cc
+++ b/lib/test.cc
@@ -14,7 +14,8 @@ NAN_METHOD(WrappedRE2::Test)
 		return;
 	}
 
-	auto str = re2->prepareArgument(info[0]);
+	PrepareLastString prep(re2, info[0]);
+	StrVal& str = prep;
 	if (str.isBad) return; // throws an exception
 
 	if (!re2->global && !re2->sticky)
diff --git a/lib/wrapped_re2.h b/lib/wrapped_re2.h
index 6a6c1c3..50ddd05 100644
--- a/lib/wrapped_re2.h
+++ b/lib/wrapped_re2.h
@@ -119,6 +119,30 @@ class WrappedRE2 : public Nan::ObjectWrap
 
 	void dropCache();
 	const StrVal &prepareArgument(const v8::Local<v8::Value> &arg, bool ignoreLastIndex = false);
+	void doneWithLastString();
+
+	friend class PrepareLastString;
+};
+
+struct PrepareLastString
+{
+	PrepareLastString(WrappedRE2 *re2, const v8::Local<v8::Value> &arg, bool ignoreLastIndex = false) : re2(re2) {
+		re2->prepareArgument(arg, ignoreLastIndex);
+	}
+
+	~PrepareLastString() {
+		re2->doneWithLastString();
+	}
+
+	operator const StrVal&() const {
+		return re2->lastStringValue;
+	}
+
+	operator StrVal&() {
+		return re2->lastStringValue;
+	}
+
+	WrappedRE2 *re2;
 };
 
 // utilities