--- a/rts/Game/WebbarBrowser.h
+++ b/rts/Game/WebbarBrowser.h
@@ -369,9 +369,12 @@
 						status = 3;
 					} else {
 						BuildInfo build(def, buildPos, (order.options >> 8) & 3);
-						build.pos = buildPos = CGameHelper::Pos2BuildPos(build, true);
+						// This is local UI admission, like GuiHandler. Synced placement
+						// testing updates nearby units' blocking maps and must only run
+						// during native execution of the command on every peer.
+						build.pos = buildPos = CGameHelper::Pos2BuildPos(build, false);
 						CFeature* feature = nullptr;
-						if (CGameHelper::TestUnitBuildSquare(build, feature, gu->myAllyTeam, true) == CGameHelper::BUILDSQUARE_BLOCKED) status = 7;
+						if (CGameHelper::TestUnitBuildSquare(build, feature, gu->myAllyTeam, false) == CGameHelper::BUILDSQUARE_BLOCKED) status = 7;
 						command = build.CreateCommand(uint8_t(order.options & SHIFT_KEY));
 					}
 				}