diff --git a/graalpython/com.oracle.graal.python/src/com/oracle/graal/python/runtime/NativePosixSupport.java b/graalpython/com.oracle.graal.python/src/com/oracle/graal/python/runtime/NativePosixSupport.java
index 6ae8ca523d..4f896333d2 100644
--- a/graalpython/com.oracle.graal.python/src/com/oracle/graal/python/runtime/NativePosixSupport.java
+++ b/graalpython/com.oracle.graal.python/src/com/oracle/graal/python/runtime/NativePosixSupport.java
@@ -2306,7 +2306,6 @@ public Object mmap(Node inliningTarget, long length, int prot, int flags, int fd
     }
 
     @Override
-    @TruffleBoundary
     @SuppressWarnings("static-method")
     public byte mmapReadByte(Object mmap, long index) {
         MMapHandle handle = (MMapHandle) mmap;
@@ -2318,7 +2317,6 @@ public byte mmapReadByte(Object mmap, long index) {
     }
 
     @Override
-    @TruffleBoundary
     @SuppressWarnings("static-method")
     public void mmapWriteByte(Object mmap, long index, byte value) {
         MMapHandle handle = (MMapHandle) mmap;
@@ -2327,7 +2325,6 @@ public void mmapWriteByte(Object mmap, long index, byte value) {
     }
 
     @Override
-    @TruffleBoundary
     @SuppressWarnings("static-method")
     public int mmapReadBytes(Object mmap, long index, byte[] bytes, int length) {
         MMapHandle handle = (MMapHandle) mmap;
@@ -2337,7 +2334,6 @@ public int mmapReadBytes(Object mmap, long index, byte[] bytes, int length) {
     }
 
     @Override
-    @TruffleBoundary
     @SuppressWarnings("static-method")
     public void mmapWriteBytes(Object mmap, long index, byte[] bytes, int length) {
         MMapHandle handle = (MMapHandle) mmap;
@@ -2368,7 +2364,6 @@ public void mmapUnmap(Object mmap, long length) throws PosixException {
     }
 
     @Override
-    @TruffleBoundary
     @SuppressWarnings("static-method")
     public long mmapGetPointer(Object mmap) {
         MMapHandle handle = (MMapHandle) mmap;
diff --git a/graalpython/com.oracle.graal.python/src/com/oracle/graal/python/runtime/PosixSupport.java b/graalpython/com.oracle.graal.python/src/com/oracle/graal/python/runtime/PosixSupport.java
index c544c12f01..aa22264602 100644
--- a/graalpython/com.oracle.graal.python/src/com/oracle/graal/python/runtime/PosixSupport.java
+++ b/graalpython/com.oracle.graal.python/src/com/oracle/graal/python/runtime/PosixSupport.java
@@ -73,7 +73,8 @@ public abstract class PosixSupport {
      * warnings. After devirtualization, partial evaluation sees the concrete implementation, which
      * needs its own annotation because method annotations are not inherited. TruffleString
      * conversions that benefit from partial evaluation belong in PosixSupportNodes, outside these
-     * boundaries.
+     * boundaries. The mmap memory access methods are an exception: the native backend performs
+     * direct memory accesses that must remain visible to partial evaluation.
      */
 
     public static final int ST_MODE = 0;
@@ -932,16 +933,14 @@ public abstract int forkExec(Object[] executables, Object[] args, Object cwd, Ob
     @TruffleBoundary
     public abstract Object mmap(Node location, long length, int prot, int flags, int fd, long offset, Object tagname) throws PosixException;
 
-    @TruffleBoundary
+    // Keep memory accesses and pointer extraction visible to partial evaluation in the native
+    // backend and its pre-initialization wrapper. Other backends may still use boundaries.
     public abstract byte mmapReadByte(Object mmap, long index) throws PosixException;
 
-    @TruffleBoundary
     public abstract void mmapWriteByte(Object mmap, long index, byte value) throws PosixException;
 
-    @TruffleBoundary
     public abstract int mmapReadBytes(Object mmap, long index, byte[] bytes, int length) throws PosixException;
 
-    @TruffleBoundary
     public abstract void mmapWriteBytes(Object mmap, long index, byte[] bytes, int length) throws PosixException;
 
     @TruffleBoundary
@@ -950,7 +949,6 @@ public abstract int forkExec(Object[] executables, Object[] args, Object cwd, Ob
     @TruffleBoundary
     public abstract void mmapUnmap(Object mmap, long length) throws PosixException;
 
-    @TruffleBoundary
     public abstract long mmapGetPointer(Object mmap) throws UnsupportedPosixFeatureException;
 
     @TruffleBoundary
diff --git a/graalpython/com.oracle.graal.python/src/com/oracle/graal/python/runtime/PreInitPosixSupport.java b/graalpython/com.oracle.graal.python/src/com/oracle/graal/python/runtime/PreInitPosixSupport.java
index 7063169eef..c5123198e3 100644
--- a/graalpython/com.oracle.graal.python/src/com/oracle/graal/python/runtime/PreInitPosixSupport.java
+++ b/graalpython/com.oracle.graal.python/src/com/oracle/graal/python/runtime/PreInitPosixSupport.java
@@ -907,28 +907,24 @@ public final Object mmap(Node location, long length, int prot, int flags, int fd
     }
 
     @Override
-    @TruffleBoundary
     public final byte mmapReadByte(Object mmap, long index) throws PosixException {
         checkNotInPreInitialization();
         return nativePosixSupport.mmapReadByte(mmap, index);
     }
 
     @Override
-    @TruffleBoundary
     public final void mmapWriteByte(Object mmap, long index, byte value) throws PosixException {
         checkNotInPreInitialization();
         nativePosixSupport.mmapWriteByte(mmap, index, value);
     }
 
     @Override
-    @TruffleBoundary
     public final int mmapReadBytes(Object mmap, long index, byte[] bytes, int length) throws PosixException {
         checkNotInPreInitialization();
         return nativePosixSupport.mmapReadBytes(mmap, index, bytes, length);
     }
 
     @Override
-    @TruffleBoundary
     public final void mmapWriteBytes(Object mmap, long index, byte[] bytes, int length) throws PosixException {
         checkNotInPreInitialization();
         nativePosixSupport.mmapWriteBytes(mmap, index, bytes, length);
@@ -949,7 +945,6 @@ public final void mmapUnmap(Object mmap, long length) throws PosixException {
     }
 
     @Override
-    @TruffleBoundary
     public final long mmapGetPointer(Object mmap) throws UnsupportedPosixFeatureException {
         checkNotInPreInitialization();
         return nativePosixSupport.mmapGetPointer(mmap);