diff --git a/cpp/ql/lib/semmle/code/cpp/ir/implementation/aliased_ssa/IRBlock.qll b/cpp/ql/lib/semmle/code/cpp/ir/implementation/aliased_ssa/IRBlock.qll
index 82db3146630..bac7634cbd0 100644
--- a/cpp/ql/lib/semmle/code/cpp/ir/implementation/aliased_ssa/IRBlock.qll
+++ b/cpp/ql/lib/semmle/code/cpp/ir/implementation/aliased_ssa/IRBlock.qll
@@ -161,8 +161,13 @@ class IRBlock extends IRBlockBase {
    */
   pragma[noinline]
   final IRBlock dominanceFrontier() {
-    this.dominates(result.getAPredecessor()) and
-    not this.strictlyDominates(result)
+    this.getASuccessor() = result and
+    not this.immediatelyDominates(result)
+    or
+    exists(IRBlock prev | result = prev.dominanceFrontier() |
+      this.immediatelyDominates(prev) and
+      not this.immediatelyDominates(result)
+    )
   }
 
   /**
@@ -201,8 +206,13 @@ class IRBlock extends IRBlockBase {
    */
   pragma[noinline]
   final IRBlock postDominanceFrontier() {
-    this.postDominates(result.getASuccessor()) and
-    not this.strictlyPostDominates(result)
+    this.getAPredecessor() = result and
+    not this.immediatelyPostDominates(result)
+    or
+    exists(IRBlock prev | result = prev.postDominanceFrontier() |
+      this.immediatelyPostDominates(prev) and
+      not this.immediatelyPostDominates(result)
+    )
   }
 
   /**
diff --git a/cpp/ql/lib/semmle/code/cpp/ir/implementation/raw/IRBlock.qll b/cpp/ql/lib/semmle/code/cpp/ir/implementation/raw/IRBlock.qll
index 82db3146630..bac7634cbd0 100644
--- a/cpp/ql/lib/semmle/code/cpp/ir/implementation/raw/IRBlock.qll
+++ b/cpp/ql/lib/semmle/code/cpp/ir/implementation/raw/IRBlock.qll
@@ -161,8 +161,13 @@ class IRBlock extends IRBlockBase {
    */
   pragma[noinline]
   final IRBlock dominanceFrontier() {
-    this.dominates(result.getAPredecessor()) and
-    not this.strictlyDominates(result)
+    this.getASuccessor() = result and
+    not this.immediatelyDominates(result)
+    or
+    exists(IRBlock prev | result = prev.dominanceFrontier() |
+      this.immediatelyDominates(prev) and
+      not this.immediatelyDominates(result)
+    )
   }
 
   /**
@@ -201,8 +206,13 @@ class IRBlock extends IRBlockBase {
    */
   pragma[noinline]
   final IRBlock postDominanceFrontier() {
-    this.postDominates(result.getASuccessor()) and
-    not this.strictlyPostDominates(result)
+    this.getAPredecessor() = result and
+    not this.immediatelyPostDominates(result)
+    or
+    exists(IRBlock prev | result = prev.postDominanceFrontier() |
+      this.immediatelyPostDominates(prev) and
+      not this.immediatelyPostDominates(result)
+    )
   }
 
   /**
diff --git a/cpp/ql/lib/semmle/code/cpp/ir/implementation/unaliased_ssa/IRBlock.qll b/cpp/ql/lib/semmle/code/cpp/ir/implementation/unaliased_ssa/IRBlock.qll
index 82db3146630..bac7634cbd0 100644
--- a/cpp/ql/lib/semmle/code/cpp/ir/implementation/unaliased_ssa/IRBlock.qll
+++ b/cpp/ql/lib/semmle/code/cpp/ir/implementation/unaliased_ssa/IRBlock.qll
@@ -161,8 +161,13 @@ class IRBlock extends IRBlockBase {
    */
   pragma[noinline]
   final IRBlock dominanceFrontier() {
-    this.dominates(result.getAPredecessor()) and
-    not this.strictlyDominates(result)
+    this.getASuccessor() = result and
+    not this.immediatelyDominates(result)
+    or
+    exists(IRBlock prev | result = prev.dominanceFrontier() |
+      this.immediatelyDominates(prev) and
+      not this.immediatelyDominates(result)
+    )
   }
 
   /**
@@ -201,8 +206,13 @@ class IRBlock extends IRBlockBase {
    */
   pragma[noinline]
   final IRBlock postDominanceFrontier() {
-    this.postDominates(result.getASuccessor()) and
-    not this.strictlyPostDominates(result)
+    this.getAPredecessor() = result and
+    not this.immediatelyPostDominates(result)
+    or
+    exists(IRBlock prev | result = prev.postDominanceFrontier() |
+      this.immediatelyPostDominates(prev) and
+      not this.immediatelyPostDominates(result)
+    )
   }
 
   /**
diff --git a/csharp/ql/src/experimental/ir/implementation/raw/IRBlock.qll b/csharp/ql/src/experimental/ir/implementation/raw/IRBlock.qll
index 82db3146630..bac7634cbd0 100644
--- a/csharp/ql/src/experimental/ir/implementation/raw/IRBlock.qll
+++ b/csharp/ql/src/experimental/ir/implementation/raw/IRBlock.qll
@@ -161,8 +161,13 @@ class IRBlock extends IRBlockBase {
    */
   pragma[noinline]
   final IRBlock dominanceFrontier() {
-    this.dominates(result.getAPredecessor()) and
-    not this.strictlyDominates(result)
+    this.getASuccessor() = result and
+    not this.immediatelyDominates(result)
+    or
+    exists(IRBlock prev | result = prev.dominanceFrontier() |
+      this.immediatelyDominates(prev) and
+      not this.immediatelyDominates(result)
+    )
   }
 
   /**
@@ -201,8 +206,13 @@ class IRBlock extends IRBlockBase {
    */
   pragma[noinline]
   final IRBlock postDominanceFrontier() {
-    this.postDominates(result.getASuccessor()) and
-    not this.strictlyPostDominates(result)
+    this.getAPredecessor() = result and
+    not this.immediatelyPostDominates(result)
+    or
+    exists(IRBlock prev | result = prev.postDominanceFrontier() |
+      this.immediatelyPostDominates(prev) and
+      not this.immediatelyPostDominates(result)
+    )
   }
 
   /**
diff --git a/csharp/ql/src/experimental/ir/implementation/unaliased_ssa/IRBlock.qll b/csharp/ql/src/experimental/ir/implementation/unaliased_ssa/IRBlock.qll
index 82db3146630..bac7634cbd0 100644
--- a/csharp/ql/src/experimental/ir/implementation/unaliased_ssa/IRBlock.qll
+++ b/csharp/ql/src/experimental/ir/implementation/unaliased_ssa/IRBlock.qll
@@ -161,8 +161,13 @@ class IRBlock extends IRBlockBase {
    */
   pragma[noinline]
   final IRBlock dominanceFrontier() {
-    this.dominates(result.getAPredecessor()) and
-    not this.strictlyDominates(result)
+    this.getASuccessor() = result and
+    not this.immediatelyDominates(result)
+    or
+    exists(IRBlock prev | result = prev.dominanceFrontier() |
+      this.immediatelyDominates(prev) and
+      not this.immediatelyDominates(result)
+    )
   }
 
   /**
@@ -201,8 +206,13 @@ class IRBlock extends IRBlockBase {
    */
   pragma[noinline]
   final IRBlock postDominanceFrontier() {
-    this.postDominates(result.getASuccessor()) and
-    not this.strictlyPostDominates(result)
+    this.getAPredecessor() = result and
+    not this.immediatelyPostDominates(result)
+    or
+    exists(IRBlock prev | result = prev.postDominanceFrontier() |
+      this.immediatelyPostDominates(prev) and
+      not this.immediatelyPostDominates(result)
+    )
   }
 
   /**