diff --git a/src/core/compileAssign.go b/src/core/compileAssign.go
index 6119b7f..37e751b 100644
--- a/src/core/compileAssign.go
+++ b/src/core/compileAssign.go
@@ -33,6 +33,10 @@ func (f *Function) compileAssign(node *ast.Assign) error {
 		return err
 	}
 
+	if f.IsIdentified(rightValue) {
+		rightValue = f.copy(rightValue, ssa.Source(right.Source()))
+	}
+
 	if node.Expression.Token.Kind == token.Assign {
 		f.Block().Identify(name, rightValue)
 		return nil
diff --git a/src/core/compileDefinition.go b/src/core/compileDefinition.go
index 7a0fefa..0f4ca08 100644
--- a/src/core/compileDefinition.go
+++ b/src/core/compileDefinition.go
@@ -29,7 +29,6 @@ func (f *Function) compileDefinition(node *ast.Define) error {
 		return err
 	}
 
-	block := f.Block()
 	structure, isStructType := value.Type().(*types.Struct)
 
 	// If the value we got was a value that is stored in a variable,
@@ -37,7 +36,7 @@ func (f *Function) compileDefinition(node *ast.Define) error {
 	// We want to assure that every named variable creates a copy of
 	// another named variable instead of using the cached value itself
 	// because it could lead to incorrect optimizations.
-	if !isStructType && block.IsIdentified(value) {
+	if !isStructType && f.IsIdentified(value) {
 		value = f.copy(value, ssa.Source(right.Source()))
 	}
 
diff --git a/src/ssa/IR.go b/src/ssa/IR.go
index a0e3752..c349591 100644
--- a/src/ssa/IR.go
+++ b/src/ssa/IR.go
@@ -47,6 +47,17 @@ func (f *IR) Finalize() {
 	}
 }
 
+// IsIdentified returns true if the value can be obtained from one of the identifiers.
+func (f *IR) IsIdentified(value Value) bool {
+	for _, block := range f.Blocks {
+		if block.IsIdentified(value) {
+			return true
+		}
+	}
+
+	return false
+}
+
 // Values yields on each value.
 func (f *IR) Values(yield func(int, Value) bool) {
 	index := 0
diff --git a/tests/fibonacci.q b/tests/fibonacci.q
new file mode 100644
index 0000000..425f00e
--- /dev/null
+++ b/tests/fibonacci.q
@@ -0,0 +1,26 @@
+main() {
+	loop i := 0..10 {
+		assert fib1(i) == fib2(i)
+	}
+}
+
+fib1(n int) -> int {
+	b := 0
+	c := 1
+
+	loop 0..n {
+		a := b
+		b = c
+		c = a + b
+	}
+
+	return b
+}
+
+fib2(n int) -> int {
+	if n <= 1 {
+		return n
+	}
+
+	return fib2(n - 1) + fib2(n - 2)
+}
\ No newline at end of file