diff --git a/cpp/ql/src/semmle/code/cpp/ir/implementation/Opcode.qll b/cpp/ql/src/semmle/code/cpp/ir/implementation/Opcode.qll
index 33bb0895d8c..83c9ac1215c 100644
--- a/cpp/ql/src/semmle/code/cpp/ir/implementation/Opcode.qll
+++ b/cpp/ql/src/semmle/code/cpp/ir/implementation/Opcode.qll
@@ -214,23 +214,28 @@ abstract class IndirectReadOpcode extends IndirectMemoryAccessOpcode {
 }
 
 /**
- * An opcode that accesses a memory buffer of unknown size.
+ * An opcode that accesses a memory buffer.
  */
 abstract class BufferAccessOpcode extends Opcode {
   final override predicate hasAddressOperand() { any() }
 }
 
+/**
+ * An opcode that accesses a memory buffer of unknown size.
+ */
+abstract class UnsizedBufferAccessOpcode extends BufferAccessOpcode { }
+
 /**
  * An opcode that writes to a memory buffer of unknown size.
  */
-abstract class BufferWriteOpcode extends BufferAccessOpcode {
+abstract class UnsizedBufferWriteOpcode extends UnsizedBufferAccessOpcode {
   final override MemoryAccessKind getWriteMemoryAccess() { result instanceof BufferMemoryAccess }
 }
 
 /**
  * An opcode that reads from a memory buffer of unknown size.
  */
-abstract class BufferReadOpcode extends BufferAccessOpcode {
+abstract class UnsizedBufferReadOpcode extends UnsizedBufferAccessOpcode {
   final override MemoryAccessKind getReadMemoryAccess() { result instanceof BufferMemoryAccess }
 }
 
@@ -262,9 +267,7 @@ abstract class EntireAllocationReadOpcode extends EntireAllocationAccessOpcode {
 /**
  * An opcode that accesses a memory buffer whose size is determined by a `BufferSizeOperand`.
  */
-abstract class SizedBufferAccessOpcode extends Opcode {
-  final override predicate hasAddressOperand() { any() }
-
+abstract class SizedBufferAccessOpcode extends BufferAccessOpcode {
   final override predicate hasBufferSizeOperand() { any() }
 }
 
@@ -667,17 +670,18 @@ module Opcode {
     final override string toString() { result = "IndirectMayWriteSideEffect" }
   }
 
-  class BufferReadSideEffect extends ReadSideEffectOpcode, BufferReadOpcode, TBufferReadSideEffect {
+  class BufferReadSideEffect extends ReadSideEffectOpcode, UnsizedBufferReadOpcode,
+    TBufferReadSideEffect {
     final override string toString() { result = "BufferReadSideEffect" }
   }
 
-  class BufferMustWriteSideEffect extends WriteSideEffectOpcode, BufferWriteOpcode,
+  class BufferMustWriteSideEffect extends WriteSideEffectOpcode, UnsizedBufferWriteOpcode,
     TBufferMustWriteSideEffect {
     final override string toString() { result = "BufferMustWriteSideEffect" }
   }
 
-  class BufferMayWriteSideEffect extends WriteSideEffectOpcode, BufferWriteOpcode, MayWriteOpcode,
-    TBufferMayWriteSideEffect {
+  class BufferMayWriteSideEffect extends WriteSideEffectOpcode, UnsizedBufferWriteOpcode,
+    MayWriteOpcode, TBufferMayWriteSideEffect {
     final override string toString() { result = "BufferMayWriteSideEffect" }
   }
 
diff --git a/cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/AliasedSSA.qll b/cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/AliasedSSA.qll
index cb55ec0924c..e754e8d3849 100644
--- a/cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/AliasedSSA.qll
+++ b/cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/internal/AliasedSSA.qll
@@ -26,7 +26,7 @@ private predicate hasResultMemoryAccess(
     type = languageType.getIRType() and
     isIndirectOrBufferMemoryAccess(instr.getResultMemoryAccess()) and
     (if instr.hasResultMayMemoryAccess() then isMayAccess = true else isMayAccess = false) and
-    if type.getByteSize() > 0
+    if exists(type.getByteSize())
     then endBitOffset = Ints::add(startBitOffset, Ints::mul(type.getByteSize(), 8))
     else endBitOffset = Ints::unknown()
   )
@@ -43,7 +43,7 @@ private predicate hasOperandMemoryAccess(
     type = languageType.getIRType() and
     isIndirectOrBufferMemoryAccess(operand.getMemoryAccess()) and
     (if operand.hasMayReadMemoryAccess() then isMayAccess = true else isMayAccess = false) and
-    if type.getByteSize() > 0
+    if exists(type.getByteSize())
     then endBitOffset = Ints::add(startBitOffset, Ints::mul(type.getByteSize(), 8))
     else endBitOffset = Ints::unknown()
   )
diff --git a/cpp/ql/src/semmle/code/cpp/ir/implementation/raw/internal/TranslatedCall.qll b/cpp/ql/src/semmle/code/cpp/ir/implementation/raw/internal/TranslatedCall.qll
index ba763a4c03c..fb7dc173812 100644
--- a/cpp/ql/src/semmle/code/cpp/ir/implementation/raw/internal/TranslatedCall.qll
+++ b/cpp/ql/src/semmle/code/cpp/ir/implementation/raw/internal/TranslatedCall.qll
@@ -503,7 +503,7 @@ class TranslatedSideEffect extends TranslatedElement, TTranslatedArgumentSideEff
   }
 
   override CppType getInstructionOperandType(InstructionTag tag, TypedOperandTag operandTag) {
-    if hasSpecificReadSideEffect(any(Opcode::BufferReadSideEffect op))
+    if hasSpecificReadSideEffect(any(BufferAccessOpcode op))
     then
       result = getUnknownType() and
       tag instanceof OnlyInstructionTag and
diff --git a/csharp/ql/src/semmle/code/csharp/ir/implementation/Opcode.qll b/csharp/ql/src/semmle/code/csharp/ir/implementation/Opcode.qll
index 33bb0895d8c..83c9ac1215c 100644
--- a/csharp/ql/src/semmle/code/csharp/ir/implementation/Opcode.qll
+++ b/csharp/ql/src/semmle/code/csharp/ir/implementation/Opcode.qll
@@ -214,23 +214,28 @@ abstract class IndirectReadOpcode extends IndirectMemoryAccessOpcode {
 }
 
 /**
- * An opcode that accesses a memory buffer of unknown size.
+ * An opcode that accesses a memory buffer.
  */
 abstract class BufferAccessOpcode extends Opcode {
   final override predicate hasAddressOperand() { any() }
 }
 
+/**
+ * An opcode that accesses a memory buffer of unknown size.
+ */
+abstract class UnsizedBufferAccessOpcode extends BufferAccessOpcode { }
+
 /**
  * An opcode that writes to a memory buffer of unknown size.
  */
-abstract class BufferWriteOpcode extends BufferAccessOpcode {
+abstract class UnsizedBufferWriteOpcode extends UnsizedBufferAccessOpcode {
   final override MemoryAccessKind getWriteMemoryAccess() { result instanceof BufferMemoryAccess }
 }
 
 /**
  * An opcode that reads from a memory buffer of unknown size.
  */
-abstract class BufferReadOpcode extends BufferAccessOpcode {
+abstract class UnsizedBufferReadOpcode extends UnsizedBufferAccessOpcode {
   final override MemoryAccessKind getReadMemoryAccess() { result instanceof BufferMemoryAccess }
 }
 
@@ -262,9 +267,7 @@ abstract class EntireAllocationReadOpcode extends EntireAllocationAccessOpcode {
 /**
  * An opcode that accesses a memory buffer whose size is determined by a `BufferSizeOperand`.
  */
-abstract class SizedBufferAccessOpcode extends Opcode {
-  final override predicate hasAddressOperand() { any() }
-
+abstract class SizedBufferAccessOpcode extends BufferAccessOpcode {
   final override predicate hasBufferSizeOperand() { any() }
 }
 
@@ -667,17 +670,18 @@ module Opcode {
     final override string toString() { result = "IndirectMayWriteSideEffect" }
   }
 
-  class BufferReadSideEffect extends ReadSideEffectOpcode, BufferReadOpcode, TBufferReadSideEffect {
+  class BufferReadSideEffect extends ReadSideEffectOpcode, UnsizedBufferReadOpcode,
+    TBufferReadSideEffect {
     final override string toString() { result = "BufferReadSideEffect" }
   }
 
-  class BufferMustWriteSideEffect extends WriteSideEffectOpcode, BufferWriteOpcode,
+  class BufferMustWriteSideEffect extends WriteSideEffectOpcode, UnsizedBufferWriteOpcode,
     TBufferMustWriteSideEffect {
     final override string toString() { result = "BufferMustWriteSideEffect" }
   }
 
-  class BufferMayWriteSideEffect extends WriteSideEffectOpcode, BufferWriteOpcode, MayWriteOpcode,
-    TBufferMayWriteSideEffect {
+  class BufferMayWriteSideEffect extends WriteSideEffectOpcode, UnsizedBufferWriteOpcode,
+    MayWriteOpcode, TBufferMayWriteSideEffect {
     final override string toString() { result = "BufferMayWriteSideEffect" }
   }