diff --git a/src/peakrdl_busdecoder/cpuif/apb4/apb4_cpuif_flat.py b/src/peakrdl_busdecoder/cpuif/apb4/apb4_cpuif_flat.py
index 17ec392..56ed87f 100644
--- a/src/peakrdl_busdecoder/cpuif/apb4/apb4_cpuif_flat.py
+++ b/src/peakrdl_busdecoder/cpuif/apb4/apb4_cpuif_flat.py
@@ -2,7 +2,7 @@ from typing import TYPE_CHECKING
 
 from systemrdl.node import AddressableNode
 
-from ...utils import get_indexed_path
+from ...utils import clog2, get_indexed_path
 from ..base_cpuif import BaseCpuif
 from .apb4_interface import APB4FlatInterface
 
@@ -42,7 +42,7 @@ class APB4CpuifFlat(BaseCpuif):
         fanout[self.signal("PWRITE", node, "gi")] = (
             f"cpuif_wr_sel.{get_indexed_path(self.exp.ds.top_node, node, 'gi')}"
         )
-        fanout[self.signal("PADDR", node, "gi")] = self.signal("PADDR")
+        fanout[self.signal("PADDR", node, "gi")] = f"{self.signal('PADDR')}[{clog2(node.size) - 1}:0]"
         fanout[self.signal("PPROT", node, "gi")] = self.signal("PPROT")
         fanout[self.signal("PWDATA", node, "gi")] = "cpuif_wr_data"
         fanout[self.signal("PSTRB", node, "gi")] = "cpuif_wr_byte_en"
diff --git a/src/peakrdl_busdecoder/cpuif/apb4/apb4_interface.py b/src/peakrdl_busdecoder/cpuif/apb4/apb4_interface.py
index be87240..3ad19fb 100644
--- a/src/peakrdl_busdecoder/cpuif/apb4/apb4_interface.py
+++ b/src/peakrdl_busdecoder/cpuif/apb4/apb4_interface.py
@@ -2,6 +2,7 @@
 
 from systemrdl.node import AddressableNode
 
+from ...utils import clog2
 from ..interface import FlatInterface, SVInterface
 
 
@@ -50,7 +51,7 @@ class APB4FlatInterface(FlatInterface):
             f"output logic {self.signal('PSEL', child)}",
             f"output logic {self.signal('PENABLE', child)}",
             f"output logic {self.signal('PWRITE', child)}",
-            f"output logic [{self.cpuif.addr_width - 1}:0] {self.signal('PADDR', child)}",
+            f"output logic [{clog2(child.size) - 1}:0] {self.signal('PADDR', child)}",
             f"output logic [2:0] {self.signal('PPROT', child)}",
             f"output logic [{self.cpuif.data_width - 1}:0] {self.signal('PWDATA', child)}",
             f"output logic [{self.cpuif.data_width // 8 - 1}:0] {self.signal('PSTRB', child)}",