diff --git a/firmware/application/hw/max2839.cpp b/firmware/application/hw/max2839.cpp
index 7243bab95..9286ac7db 100644
--- a/firmware/application/hw/max2839.cpp
+++ b/firmware/application/hw/max2839.cpp
@@ -307,9 +307,8 @@ void MAX2839::configure_rx_gain() {
     }
 
     _map.r.lpf_vga_2.L = lna::gain_ordinal(lna_gain);
-    _dirty[Register::RXRF_2] = 1;
     _map.r.lpf_vga_2.VGA = vga::gain_ordinal(vga_gain);
-    _dirty[Register::LPF_VGA_2] = 1;
+    _dirty[Register::LPF_VGA_2] = 1; /* both L (LNA) and VGA live in LPF_VGA_2 */
     flush();
 }
 
diff --git a/firmware/baseband/CMakeLists.txt b/firmware/baseband/CMakeLists.txt
index 4bd84258b..c5939a12b 100644
--- a/firmware/baseband/CMakeLists.txt
+++ b/firmware/baseband/CMakeLists.txt
@@ -220,11 +220,17 @@ endif()
 
 # Upstream hackrf headers now gate on IS_* macros normally populated by
 # hackrf/firmware/platform-detect.cmake. We don't include that here, so derive
-# the IS_* set from BOARD ourselves. IS_H1_R9 is forced to 0 (compile-time
-# constant) so `if (IS_H1_R9)` branches resolve without needing the runtime
-# detected_platform() symbol, which mayhem doesn't link in.
+# the IS_* set from BOARD ourselves. IS_H1_R9 must mirror the upstream
+# HACKRF_ONE definition: a *runtime* check on detected_platform(). The only
+# baseband image that compiles IS_H1_R9-gated upstream files (rf_path.c,
+# si5351c.c, sgpio.c, platform_gpio.c, platform_scu.c) is sd_over_usb, which
+# does link platform_detect.c and calls detect_hardware_platform() at startup.
+# Forcing IS_H1_R9=0 here silently compiled out all H1R9 behaviour, so a real
+# HackRF One r9 was configured with the OG clock/GPIO/RF-path setup in that
+# image. All usages are `#ifdef IS_H1_R9` + `if (IS_H1_R9)` (never arithmetic
+# `#if`), so a function-call expression is safe.
 if(BOARD STREQUAL "HACKRF_ONE")
-    set(BOARD_IS_DEFS "-DIS_HACKRF_ONE=1 -DIS_NOT_PRALINE=1 -DIS_H1_R9=0 -DIS_NOT_H1_R9=1 -DIS_NOT_RAD1O=1 -DIS_NOT_JAWBREAKER=1 -DIS_H1_OR_PRALINE=1 -DIS_H1_OR_RAD1O=1 -DIS_H1_OR_JAWBREAKER=1 -DIS_EXPANSION_COMPATIBLE=1")
+    set(BOARD_IS_DEFS "-DIS_HACKRF_ONE=1 -DIS_NOT_PRALINE=1 -D'IS_H1_R9=(detected_platform()==BOARD_ID_HACKRF1_R9)' -D'IS_NOT_H1_R9=(!IS_H1_R9)' -DIS_NOT_RAD1O=1 -DIS_NOT_JAWBREAKER=1 -DIS_H1_OR_PRALINE=1 -DIS_H1_OR_RAD1O=1 -DIS_H1_OR_JAWBREAKER=1 -DIS_EXPANSION_COMPATIBLE=1")
 elseif(BOARD STREQUAL "PRALINE")
     set(BOARD_IS_DEFS "-DIS_PRALINE=1 -DIS_NOT_HACKRF_ONE=1 -DIS_NOT_H1_R9=1 -DIS_NOT_RAD1O=1 -DIS_NOT_JAWBREAKER=1 -DIS_H1_OR_PRALINE=1 -DIS_FOUR_LEDS=1 -DIS_EXPANSION_COMPATIBLE=1")
 elseif(BOARD STREQUAL "RAD1O")