diff --git a/README.md b/README.md
index b88acf6..b7b7efc 100644
--- a/README.md
+++ b/README.md
@@ -37,6 +37,8 @@ The goal is to produce idiomatic, maintainable Go code as part of a one-off conv
 [ ] Assignment expressions 
 	- Go doesn't support assignment in rvalues, only as a statement
 	- When walking below stmt level, need to first fully walk and check for any function calls + assignments that may need hoisting (and we can probably only do that correctly if there is no short-circuiting)
+	- [X] Add subtree walk + catch error for this case
+	- [ ] Add hoisting pass
 [ ] Closures
 	- [ ] Handle value/reference captures
 [ ] Sort callbacks
diff --git a/miniwalker.go b/miniwalker.go
new file mode 100644
index 0000000..5aaf623
--- /dev/null
+++ b/miniwalker.go
@@ -0,0 +1,42 @@
+package main
+
+import (
+	"fmt"
+
+	"github.com/z7zmey/php-parser/node"
+	"github.com/z7zmey/php-parser/walker"
+)
+
+type miniWalker struct {
+	cb      func(node.Node) error
+	lastErr error
+}
+
+func (mw *miniWalker) EnterNode(w walker.Walkable) bool {
+	n, ok := w.(node.Node)
+	if !ok {
+		mw.lastErr = fmt.Errorf("Tried to walk non-node '%t'", w)
+		return false
+	}
+
+	err := mw.cb(n)
+	if err != nil {
+		mw.lastErr = err
+		return false
+	}
+
+	return true
+}
+
+func (mw *miniWalker) LeaveNode(w walker.Walkable)                  {}
+func (mw *miniWalker) EnterChildNode(key string, w walker.Walkable) {}
+func (mw *miniWalker) LeaveChildNode(key string, w walker.Walkable) {}
+func (mw *miniWalker) EnterChildList(key string, w walker.Walkable) {}
+func (mw *miniWalker) LeaveChildList(key string, w walker.Walkable) {}
+
+func walk(n node.Node, cb func(node.Node) error) error {
+	mw := miniWalker{cb: cb}
+	n.Walk(&mw)
+
+	return mw.lastErr
+}
diff --git a/node.go b/node.go
index 6db7e2a..dc67dd1 100644
--- a/node.go
+++ b/node.go
@@ -511,6 +511,15 @@ func (this *conversionState) convertNoFreeFloating(n_ node.Node) (string, error)
 		return "fmt.Print(" + quoted + ")\n", nil // newline - standalone statement
 
 	case *stmt.If:
+
+		hasCondAssign, err := hasInteriorAssignment(n.Cond)
+		if err != nil {
+			return "", parseErr{n, err}
+		}
+		if hasCondAssign {
+			return "", parseErr{n.Cond, fmt.Errorf("please remove assignment from if-expression")}
+		}
+
 		cond, err := this.convert(n.Cond)
 		if err != nil {
 			return "", parseErr{n, err}
@@ -1158,3 +1167,17 @@ func (this *conversionState) convertFunctionCommon(params []node.Node, returnTyp
 	// No extra trailing newline in case this is part of a large expression
 	return ret, nil
 }
+
+// hasInteriorAssignment recursively walks a node, to determine if it contains
+// any assignment expressions
+func hasInteriorAssignment(n node.Node) (hasAnyAssign bool, err error) {
+
+	err = walk(n, func(n node.Node) error {
+		if _, ok := n.(*assign.Assign); ok {
+			hasAnyAssign = true
+		}
+		return nil
+	})
+
+	return // named return
+}