diff --git a/inc/TRestDetectorSignal.h b/inc/TRestDetectorSignal.h
index 10dd682d..81500b9e 100644
--- a/inc/TRestDetectorSignal.h
+++ b/inc/TRestDetectorSignal.h
@@ -166,4 +166,18 @@ class TRestDetectorSignal {
 
     ClassDef(TRestDetectorSignal, 4);
 };
+
+// Schema evolution: fSignalTime and fSignalCharge changed from vector<Float_t> to
+// vector<Double_t> in ClassDef v4 (PR#109, March 2024). Files written with ClassDef
+// version <= 3 store the float layout; these rules tell ROOT how to convert on read.
+// Note: the rules can only fire when the input file contains the StreamerInfo of the
+// on-disk version of this class. See rest-for-physics/detectorlib#125.
+#pragma read sourceClass = "TRestDetectorSignal" version = "[-3]" source =                               \
+    "std::vector<Float_t> fSignalTime" targetClass = "TRestDetectorSignal" target = "fSignalTime" code = \
+        "{ fSignalTime.assign(onfile.fSignalTime.begin(), onfile.fSignalTime.end()); }"
+
+#pragma read sourceClass = "TRestDetectorSignal" version = "[-3]" source =                                   \
+    "std::vector<Float_t> fSignalCharge" targetClass = "TRestDetectorSignal" target = "fSignalCharge" code = \
+        "{ fSignalCharge.assign(onfile.fSignalCharge.begin(), onfile.fSignalCharge.end()); }"
+
 #endif