diff --git a/Changelog.md b/Changelog.md
index d5ff1204c..da14b7d16 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -25,6 +25,7 @@ Bugfixes:
  * Allow `type(Contract).name` for abstract contracts and interfaces.
  * Type Checker: Disallow structs containing nested mapping in memory as parameters for library functions.
  * Type Checker: Disallow ``using for`` directive inside interfaces.
+ * Immutables: Disallow assigning immutables more than once during their declaration.
 
 
 ### 0.7.0 (2020-07-28)
diff --git a/libsolidity/analysis/ImmutableValidator.cpp b/libsolidity/analysis/ImmutableValidator.cpp
index 5af640e58..f6fe498ea 100644
--- a/libsolidity/analysis/ImmutableValidator.cpp
+++ b/libsolidity/analysis/ImmutableValidator.cpp
@@ -34,10 +34,12 @@ void ImmutableValidator::analyze()
 	for (ContractDefinition const* contract: linearizedContracts)
 		for (VariableDeclaration const* stateVar: contract->stateVariables())
 			if (stateVar->value())
-			{
+				m_initializedStateVariables.emplace(stateVar);
+
+	for (ContractDefinition const* contract: linearizedContracts)
+		for (VariableDeclaration const* stateVar: contract->stateVariables())
+			if (stateVar->value())
 				stateVar->value()->accept(*this);
-				solAssert(m_initializedStateVariables.emplace(stateVar).second, "");
-			}
 
 	for (ContractDefinition const* contract: linearizedContracts)
 		if (contract->constructor())
diff --git a/test/libsolidity/syntaxTests/immutable/variable_declaration_already.sol b/test/libsolidity/syntaxTests/immutable/variable_declaration_already.sol
new file mode 100644
index 000000000..6c204d05e
--- /dev/null
+++ b/test/libsolidity/syntaxTests/immutable/variable_declaration_already.sol
@@ -0,0 +1,10 @@
+contract C {
+    uint immutable z = 2;
+    uint immutable x = z = y = 3;
+    uint immutable y = 5;
+}
+// ----
+// TypeError 1581: (62-63): Immutable variables can only be initialized inline or assigned directly in the constructor.
+// TypeError 1574: (62-63): Immutable state variable already initialized.
+// TypeError 1581: (66-67): Immutable variables can only be initialized inline or assigned directly in the constructor.
+// TypeError 1574: (66-67): Immutable state variable already initialized.
diff --git a/test/libsolidity/syntaxTests/immutable/variable_declaration_value.sol b/test/libsolidity/syntaxTests/immutable/variable_declaration_value.sol
new file mode 100644
index 000000000..db8dd6494
--- /dev/null
+++ b/test/libsolidity/syntaxTests/immutable/variable_declaration_value.sol
@@ -0,0 +1,6 @@
+contract C {
+    int immutable x = x = 5;
+}
+// ----
+// TypeError 1581: (35-36): Immutable variables can only be initialized inline or assigned directly in the constructor.
+// TypeError 1574: (35-36): Immutable state variable already initialized.