diff --git a/test/libsolidity/semanticTests/underscore/as_function.sol b/test/libsolidity/semanticTests/underscore/as_function.sol
new file mode 100644
index 000000000..fe18f3d90
--- /dev/null
+++ b/test/libsolidity/semanticTests/underscore/as_function.sol
@@ -0,0 +1,20 @@
+contract C {
+    function _() public pure returns (uint) {
+        return 88;
+    }
+
+    function g() public pure returns (uint){
+        return _();
+    }
+
+    function h() public pure returns (uint) {
+        _;
+        return 33;
+    }
+}
+// ====
+// compileViaYul: also
+// ----
+// _() -> 88
+// g() -> 88
+// h() -> 33
diff --git a/test/libsolidity/semanticTests/underscore/in_function.sol b/test/libsolidity/semanticTests/underscore/in_function.sol
new file mode 100644
index 000000000..9d116cb8b
--- /dev/null
+++ b/test/libsolidity/semanticTests/underscore/in_function.sol
@@ -0,0 +1,16 @@
+contract C {
+    function f() public pure returns (uint) {
+        uint _;
+        return _;
+    }
+
+    function g() public pure returns (uint) {
+        uint _ = 1;
+        return _;
+    }
+}
+// ====
+// compileViaYul: also
+// ----
+// f() -> 0
+// g() -> 1
diff --git a/test/libsolidity/semanticTests/underscore/in_modifier.sol b/test/libsolidity/semanticTests/underscore/in_modifier.sol
new file mode 100644
index 000000000..7f04c43b0
--- /dev/null
+++ b/test/libsolidity/semanticTests/underscore/in_modifier.sol
@@ -0,0 +1,23 @@
+contract C {
+    modifier m() {
+        _;
+    }
+
+    modifier n() {
+        string memory _ = "failed";
+        _;
+        revert(_);
+    }
+
+    function f() m() public returns (uint) {
+        return 88;
+    }
+
+    function g() n() public returns (uint) {
+    }
+}
+// ====
+// EVMVersion: >=byzantium
+// ----
+// f() -> 88
+// g() -> FAILURE, hex"08c379a0", 0x20, 6, "failed"
diff --git a/test/libsolidity/syntaxTests/underscore/as_function.sol b/test/libsolidity/syntaxTests/underscore/as_function.sol
new file mode 100644
index 000000000..ef8e59f27
--- /dev/null
+++ b/test/libsolidity/syntaxTests/underscore/as_function.sol
@@ -0,0 +1,12 @@
+contract C {
+    function _() public pure {
+    }
+
+    function g() public pure {
+        _();
+    }
+
+    function h() public pure {
+        _;
+    }
+}
diff --git a/test/libsolidity/syntaxTests/underscore/in_function.sol b/test/libsolidity/syntaxTests/underscore/in_function.sol
new file mode 100644
index 000000000..cd1db69f2
--- /dev/null
+++ b/test/libsolidity/syntaxTests/underscore/in_function.sol
@@ -0,0 +1,17 @@
+contract C {
+    function f() public pure returns (uint) {
+        uint _;
+        return _;
+    }
+
+    function g() public pure returns (uint) {
+        uint _ = 1;
+        return _;
+    }
+
+    function h() public pure {
+        _;
+    }
+}
+// ----
+// DeclarationError 7576: (230-231): Undeclared identifier.
diff --git a/test/libsolidity/syntaxTests/underscore/in_modifier.sol b/test/libsolidity/syntaxTests/underscore/in_modifier.sol
new file mode 100644
index 000000000..2724fc724
--- /dev/null
+++ b/test/libsolidity/syntaxTests/underscore/in_modifier.sol
@@ -0,0 +1,18 @@
+contract C {
+    modifier m() {
+        _;
+    }
+
+    modifier n() {
+        string memory _ = "";
+        _;
+        revert(_);
+    }
+
+    function f() m() public {
+    }
+
+    function g() n() public {
+    }
+}
+// ----