diff --git a/Zend/Optimizer/sccp.c b/Zend/Optimizer/sccp.c
index f17c17e9bf0..bbf52d8cf69 100644
--- a/Zend/Optimizer/sccp.c
+++ b/Zend/Optimizer/sccp.c
@@ -2037,7 +2037,7 @@ static void join_phi_values(zval *a, zval *b, bool escape) {
 	}
 }
 
-static void sccp_visit_phi(scdf_ctx *scdf, zend_ssa_phi *phi) {
+static void sccp_visit_phi(scdf_ctx *scdf, const zend_ssa_phi *phi) {
 	sccp_ctx *ctx = (sccp_ctx *) scdf;
 	zend_ssa *ssa = scdf->ssa;
 	ZEND_ASSERT(phi->ssa_var >= 0);
diff --git a/Zend/Optimizer/scdf.c b/Zend/Optimizer/scdf.c
index 550c8cf7b6f..e5c40b8c90c 100644
--- a/Zend/Optimizer/scdf.c
+++ b/Zend/Optimizer/scdf.c
@@ -71,8 +71,7 @@ void scdf_mark_edge_feasible(scdf_ctx *scdf, int from, int to) {
 		/* Block is already executable, only a new edge became feasible.
 		 * Reevaluate phi nodes to account for changed source operands. */
 		const zend_ssa_block *ssa_block = &scdf->ssa->blocks[to];
-		zend_ssa_phi *phi;
-		for (phi = ssa_block->phis; phi; phi = phi->next) {
+		for (const zend_ssa_phi *phi = ssa_block->phis; phi; phi = phi->next) {
 			zend_bitset_excl(scdf->phi_var_worklist, phi->ssa_var);
 			scdf->handlers.visit_phi(scdf, phi);
 		}
@@ -109,7 +108,7 @@ void scdf_solve(scdf_ctx *scdf, const char *name) {
 	) {
 		int i;
 		while ((i = zend_bitset_pop_first(scdf->phi_var_worklist, scdf->phi_var_worklist_len)) >= 0) {
-			zend_ssa_phi *phi = ssa->vars[i].definition_phi;
+			const zend_ssa_phi *phi = ssa->vars[i].definition_phi;
 			ZEND_ASSERT(phi);
 			if (zend_bitset_in(scdf->executable_blocks, phi->block)) {
 				scdf->handlers.visit_phi(scdf, phi);
@@ -145,12 +144,9 @@ void scdf_solve(scdf_ctx *scdf, const char *name) {
 			DEBUG_PRINT("Pop block %d from worklist\n", i);
 			zend_bitset_incl(scdf->executable_blocks, i);
 
-			{
-				zend_ssa_phi *phi;
-				for (phi = ssa_block->phis; phi; phi = phi->next) {
-					zend_bitset_excl(scdf->phi_var_worklist, phi->ssa_var);
-					scdf->handlers.visit_phi(scdf, phi);
-				}
+			for (const zend_ssa_phi *phi = ssa_block->phis; phi; phi = phi->next) {
+				zend_bitset_excl(scdf->phi_var_worklist, phi->ssa_var);
+				scdf->handlers.visit_phi(scdf, phi);
 			}
 
 			if (block->len == 0) {
diff --git a/Zend/Optimizer/scdf.h b/Zend/Optimizer/scdf.h
index 67c53ef9fc1..49222880f22 100644
--- a/Zend/Optimizer/scdf.h
+++ b/Zend/Optimizer/scdf.h
@@ -39,7 +39,7 @@ typedef struct _scdf_ctx {
 		void (*visit_instr)(
 			struct _scdf_ctx *scdf, zend_op *opline, zend_ssa_op *ssa_op);
 		void (*visit_phi)(
-			struct _scdf_ctx *scdf, zend_ssa_phi *phi);
+			struct _scdf_ctx *scdf, const zend_ssa_phi *phi);
 		void (*mark_feasible_successors)(
 			struct _scdf_ctx *scdf, int block_num, zend_basic_block *block,
 			zend_op *opline, zend_ssa_op *ssa_op);