diff --git a/hapi-fhir-docs/src/main/resources/ca/uhn/hapi/fhir/changelog/5_6_0/2958-procedure-patient-consistent-error-handling.yaml b/hapi-fhir-docs/src/main/resources/ca/uhn/hapi/fhir/changelog/5_6_0/2958-procedure-patient-consistent-error-handling.yaml
new file mode 100644
index 00000000000..f90ca63a917
--- /dev/null
+++ b/hapi-fhir-docs/src/main/resources/ca/uhn/hapi/fhir/changelog/5_6_0/2958-procedure-patient-consistent-error-handling.yaml
@@ -0,0 +1,6 @@
+---
+type: fix
+issue: 2958
+jira: SMILE-643
+title: "Fixed issue where the processing of queries like Procedure?patient= before a cache search would cause the parameter key to be removed.
+Additionally, ensured that requests like Procedure?patient cause HTTP 400 Bad Request instead of HTTP 500 Internal Error."
diff --git a/hapi-fhir-jpaserver-base/src/main/java/ca/uhn/fhir/jpa/search/SearchCoordinatorSvcImpl.java b/hapi-fhir-jpaserver-base/src/main/java/ca/uhn/fhir/jpa/search/SearchCoordinatorSvcImpl.java
index 4d266271bd9..8c1303f1571 100644
--- a/hapi-fhir-jpaserver-base/src/main/java/ca/uhn/fhir/jpa/search/SearchCoordinatorSvcImpl.java
+++ b/hapi-fhir-jpaserver-base/src/main/java/ca/uhn/fhir/jpa/search/SearchCoordinatorSvcImpl.java
@@ -1014,6 +1014,9 @@ public class SearchCoordinatorSvcImpl implements ISearchCoordinatorSvc {
 						logged = true;
 						ourLog.warn("Failed during search due to invalid request: {}", t.toString());
 					}
+				}else if (t instanceof java.lang.IllegalArgumentException && t.getMessage().contentEquals("The validated expression is false")) {
+					logged = true;
+					ourLog.warn("Failed during search due to invalid request: {}", t.toString());
 				}
 
 				if (!logged) {
@@ -1028,6 +1031,8 @@ public class SearchCoordinatorSvcImpl implements ISearchCoordinatorSvc {
 				int failureCode = InternalErrorException.STATUS_CODE;
 				if (t instanceof BaseServerResponseException) {
 					failureCode = ((BaseServerResponseException) t).getStatusCode();
+				}else if(t instanceof java.lang.IllegalArgumentException && t.getMessage().contentEquals("The validated expression is false")) {
+					failureCode = Constants.STATUS_HTTP_400_BAD_REQUEST;
 				}
 
 				if (System.getProperty(UNIT_TEST_CAPTURE_STACK) != null) {
diff --git a/hapi-fhir-jpaserver-base/src/test/java/ca/uhn/fhir/jpa/provider/r4/ResourceProviderR4CacheTest.java b/hapi-fhir-jpaserver-base/src/test/java/ca/uhn/fhir/jpa/provider/r4/ResourceProviderR4CacheTest.java
index 834d93ba816..fb33fcf46da 100644
--- a/hapi-fhir-jpaserver-base/src/test/java/ca/uhn/fhir/jpa/provider/r4/ResourceProviderR4CacheTest.java
+++ b/hapi-fhir-jpaserver-base/src/test/java/ca/uhn/fhir/jpa/provider/r4/ResourceProviderR4CacheTest.java
@@ -7,7 +7,11 @@ import ca.uhn.fhir.parser.StrictErrorHandler;
 import ca.uhn.fhir.rest.api.CacheControlDirective;
 import ca.uhn.fhir.rest.api.Constants;
 import ca.uhn.fhir.rest.client.interceptor.CapturingInterceptor;
+import ca.uhn.fhir.rest.server.exceptions.BaseServerResponseException;
+import ca.uhn.fhir.rest.server.exceptions.InternalErrorException;
 import ca.uhn.fhir.rest.server.exceptions.InvalidRequestException;
+import com.ctc.wstx.shaded.msv_core.verifier.jarv.Const;
+import org.hl7.fhir.r4.model.Base;
 import org.hl7.fhir.r4.model.Bundle;
 import org.hl7.fhir.r4.model.IdType;
 import org.hl7.fhir.r4.model.Patient;
@@ -27,6 +31,7 @@ import static org.hamcrest.Matchers.lessThan;
 import static org.hamcrest.core.IsNot.not;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.hamcrest.MatcherAssert.assertThat;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.fail;
 
 public class ResourceProviderR4CacheTest extends BaseResourceProviderR4Test {
@@ -227,5 +232,32 @@ public class ResourceProviderR4CacheTest extends BaseResourceProviderR4Test {
 		assertEquals(1, resp2.getEntry().size());
 	}
 
+	@Test
+	public void testProcedurePatient(){
+		Bundle resp2 = myClient
+			.search()
+			.byUrl("Procedure")
+			.returnBundle(Bundle.class)
+			.execute();
+
+		BaseServerResponseException exception = assertThrows(BaseServerResponseException.class, () -> {myClient
+			.search()
+			.byUrl("Procedure?patient=")
+			.returnBundle(Bundle.class)
+			.execute();});
+
+		assertEquals(Constants.STATUS_HTTP_400_BAD_REQUEST, exception.getStatusCode());
+	}
+
+	@Test
+	public void testPatient(){
+		BaseServerResponseException exception = assertThrows(BaseServerResponseException.class, () -> {myClient
+			.search()
+			.byUrl("Procedure?patient=")
+			.returnBundle(Bundle.class)
+			.execute();});
+
+		assertEquals(Constants.STATUS_HTTP_400_BAD_REQUEST, exception.getStatusCode());
+	}
 
 }
diff --git a/hapi-fhir-jpaserver-searchparam/src/main/java/ca/uhn/fhir/jpa/searchparam/SearchParameterMap.java b/hapi-fhir-jpaserver-searchparam/src/main/java/ca/uhn/fhir/jpa/searchparam/SearchParameterMap.java
index 4ad522cf3be..061531f4cc1 100644
--- a/hapi-fhir-jpaserver-searchparam/src/main/java/ca/uhn/fhir/jpa/searchparam/SearchParameterMap.java
+++ b/hapi-fhir-jpaserver-searchparam/src/main/java/ca/uhn/fhir/jpa/searchparam/SearchParameterMap.java
@@ -396,11 +396,15 @@ public class SearchParameterMap implements Serializable {
 			for (List<? extends IQueryParameterType> nextValuesAndIn : nextValuesAndsIn) {
 
 				List<IQueryParameterType> nextValuesOrsOut = new ArrayList<>();
+				/*
 				for (IQueryParameterType nextValueOrIn : nextValuesAndIn) {
 					if (nextValueOrIn.getMissing() != null || isNotBlank(nextValueOrIn.getValueAsQueryToken(theCtx))) {
 						nextValuesOrsOut.add(nextValueOrIn);
 					}
 				}
+				*/
+
+				nextValuesOrsOut.addAll(nextValuesAndIn);
 
 				nextValuesOrsOut.sort(new QueryParameterTypeComparator(theCtx));