diff --git a/include/inja/node.hpp b/include/inja/node.hpp
index 1946805..6eaac54 100644
--- a/include/inja/node.hpp
+++ b/include/inja/node.hpp
@@ -143,7 +143,7 @@ public:
   Op operation;
 
   std::string name;
-  int number_args; // Should also be negative -> -1 for unknown number
+  int number_args; // Can also be negative -> -1 for unknown number
   std::vector<std::shared_ptr<ExpressionNode>> arguments;
   CallbackFunction callback;
 
diff --git a/include/inja/parser.hpp b/include/inja/parser.hpp
index 3fbbfcc..c490a22 100644
--- a/include/inja/parser.hpp
+++ b/include/inja/parser.hpp
@@ -76,6 +76,10 @@ class Parser {
     auto function = operator_stack.top();
     operator_stack.pop();
 
+    if (static_cast<int>(arguments.size()) < function->number_args) {
+      throw_parser_error("too few arguments");
+    }
+
     for (int i = 0; i < function->number_args; ++i) {
       function->arguments.insert(function->arguments.begin(), arguments.back());
       arguments.pop_back();
diff --git a/single_include/inja/inja.hpp b/single_include/inja/inja.hpp
index 2feee8b..133ac8a 100644
--- a/single_include/inja/inja.hpp
+++ b/single_include/inja/inja.hpp
@@ -483,7 +483,7 @@ public:
   Op operation;
 
   std::string name;
-  int number_args; // Should also be negative -> -1 for unknown number
+  int number_args; // Can also be negative -> -1 for unknown number
   std::vector<std::shared_ptr<ExpressionNode>> arguments;
   CallbackFunction callback;
 
@@ -1490,6 +1490,10 @@ class Parser {
     auto function = operator_stack.top();
     operator_stack.pop();
 
+    if (static_cast<int>(arguments.size()) < function->number_args) {
+      throw_parser_error("too few arguments");
+    }
+
     for (int i = 0; i < function->number_args; ++i) {
       function->arguments.insert(function->arguments.begin(), arguments.back());
       arguments.pop_back();
diff --git a/test/test-functions.cpp b/test/test-functions.cpp
index 40a9795..432d7a6 100644
--- a/test/test-functions.cpp
+++ b/test/test-functions.cpp
@@ -35,7 +35,8 @@ TEST_CASE("functions") {
     CHECK(env.render("{{ 5^3 }}", data) == "125");
     CHECK(env.render("{{ 5 + 12 + 4 * (4 - (1 + 1))^2 - 75 * 1 }}", data) == "-42");
 
-    // CHECK_THROWS_WITH(env.render("{{ +1 }}", data), "[inja.exception.render_error] (at 1:4) empty expression");
+    CHECK_THROWS_WITH(env.render("{{ +1 }}", data), "[inja.exception.parser_error] (at 1:7) too few arguments");
+    CHECK_THROWS_WITH(env.render("{{ 1 + }}", data), "[inja.exception.parser_error] (at 1:8) too few arguments");
   }
 
   SUBCASE("upper") {