diff --git a/src/btree_rum.c b/src/btree_rum.c
index dd43a3c037..f4acb174a1 100644
--- a/src/btree_rum.c
+++ b/src/btree_rum.c
@@ -17,6 +17,27 @@
 
 #include "rum.h"
 
+/*
+ * PostgreSQL's own fallthrough-attribute wrapper is not a stable target:
+ * it's pg_attribute_fallthrough() (function-call-style) through PG18,
+ * pg_fallthrough (a bare, parenless macro) from PG19 on -- and even on
+ * PG18, pg_attribute_fallthrough() is not reliably declared under every
+ * compiler/build-mode combination (e.g. it's missing under clang's
+ * -emit-llvm JIT bitcode pass). Rather than keep chasing PostgreSQL's
+ * internal macro across versions and compilers, detect compiler support
+ * for the attribute directly and supply our own wrapper. This matches
+ * exactly what PostgreSQL's own macros expand to, just without relying
+ * on PostgreSQL to declare it consistently.
+ */
+#if defined(__has_attribute)
+#if __has_attribute(fallthrough)
+#define RUM_FALLTHROUGH() __attribute__((fallthrough))
+#endif
+#endif
+#ifndef RUM_FALLTHROUGH
+#define RUM_FALLTHROUGH() ((void) 0)
+#endif
+
 #if defined(_MSC_VER) && _MSC_VER >= 1200 && _MSC_VER < 1800 // Between VC++ 6.0 and VC++ 11.0
 #include <float.h>
 #define isfinite _finite
@@ -112,7 +133,7 @@ rum_btree_extract_query(FunctionCallInfo fcinfo,
 		case BTGreaterEqualStrategyNumber:
 		case BTGreaterStrategyNumber:
 			*ptr_partialmatch = true;
-			/*FALLTHROUGH*/
+			RUM_FALLTHROUGH();
 		case BTEqualStrategyNumber:
 		case RUM_DISTANCE:
 		case RUM_LEFT_DISTANCE:
diff --git a/src/rum.h b/src/rum.h
index 7093c4082c..9b0106abbe 100644
--- a/src/rum.h
+++ b/src/rum.h
@@ -1019,7 +1019,15 @@ rumDataPageLeafRead(char *ptr, OffsetNumber attnum, RumItem * item,
 			switch (attr->attlen)
 			{
 				case sizeof(char):
-					item->addInfo = Int8GetDatum(*ptr);
+
+					/*
+					 * PG19 removed Int8GetDatum() from postgres.h.
+					 * CharGetDatum() performs the identical (Datum) (X)
+					 * byte-value conversion and remains present in every
+					 * supported PostgreSQL version, so use it instead of
+					 * depending on Int8GetDatum()'s continued existence.
+					 */
+					item->addInfo = CharGetDatum(*ptr);
 					break;
 				case sizeof(int16):
 					memcpy(&u.i16, ptr, sizeof(int16));
diff --git a/src/rumutil.c b/src/rumutil.c
index 53a8667207..bef8436d01 100644
--- a/src/rumutil.c
+++ b/src/rumutil.c
@@ -284,6 +284,20 @@ initRumState(RumState * state, Relation index)
 			{
 				state->addAttrs[i] = NULL;
 			}
+
+			/*
+			 * PG19 added a tuple-deformation offset cache to TupleDesc
+			 * (firstNonCachedOffsetAttr) that is only initialized by
+			 * TupleDescFinalize(). Any TupleDesc hand-built via
+			 * CreateTemplateTupleDesc()/TupleDescInitEntry(), as above,
+			 * must now be finalized before it is used to form or read
+			 * tuples, or PG core will hit
+			 * Assert(tupleDesc->firstNonCachedOffsetAttr >= 0) the first
+			 * time it tries to deform one -- exactly what happened here.
+			 */
+#if PG_VERSION_NUM >= 190000
+			TupleDescFinalize(state->tupdesc[i]);
+#endif
 		}
 		else
 		{
@@ -311,6 +325,11 @@ initRumState(RumState * state, Relation index)
 			{
 				state->addAttrs[i] = NULL;
 			}
+
+			/* See comment above the oneCol branch's TupleDescFinalize(). */
+#if PG_VERSION_NUM >= 190000
+			TupleDescFinalize(state->tupdesc[i]);
+#endif
 		}
 
 		/*