diff --git a/base/src/main/java/proguard/classfile/editor/CodeAttributeComposer.java b/base/src/main/java/proguard/classfile/editor/CodeAttributeComposer.java
index 80256550..ec5ed05d 100644
--- a/base/src/main/java/proguard/classfile/editor/CodeAttributeComposer.java
+++ b/base/src/main/java/proguard/classfile/editor/CodeAttributeComposer.java
@@ -291,6 +291,7 @@ public void appendInstruction(int oldInstructionOffset, Instruction instruction)
     int newCodeLength = codeLength + instruction.length(codeLength);
 
     ensureCodeLength(newCodeLength);
+    ensureFragmentLength(oldInstructionOffset + 1);
 
     // Remember the old offset of the appended instruction.
     oldInstructionOffsets[codeLength] = oldInstructionOffset;
@@ -325,6 +326,7 @@ public void appendLabel(int oldInstructionOffset) {
 
     // Make sure the code and offset arrays are large enough.
     ensureCodeLength(codeLength + 1);
+    ensureFragmentLength(oldInstructionOffset + 1);
 
     // Remember the old offset of the following instruction.
     oldInstructionOffsets[codeLength] = oldInstructionOffset;
@@ -1067,6 +1069,22 @@ private void ensureCodeLength(int newCodeLength) {
     }
   }
 
+  /** Make sure the code fragment offset array have at least the given size. */
+  private void ensureFragmentLength(int newFragmentLength) {
+    if (codeFragmentLengths[level] < newFragmentLength) {
+      codeFragmentLengths[level] = newFragmentLength;
+
+      int oldFragmentLength = instructionOffsetMap[level].length;
+      if (newFragmentLength > oldFragmentLength) {
+        // Add 20% to avoid extending the arrays too often.
+        newFragmentLength = newFragmentLength * 6 / 5;
+        instructionOffsetMap[level] =
+            ArrayUtil.extendArray(instructionOffsetMap[level], newFragmentLength);
+        Arrays.fill(instructionOffsetMap[level], oldFragmentLength, newFragmentLength, INVALID);
+      }
+    }
+  }
+
   /** Adjusts the given jump offsets for the instruction at the given offset. */
   private void updateJumpOffsets(int offset, int[] jumpOffsets) {
     for (int index = 0; index < jumpOffsets.length; index++) {