diff --git a/RELEASE_NOTES.md b/RELEASE_NOTES.md
index 007ac857a..e69de29bb 100644
--- a/RELEASE_NOTES.md
+++ b/RELEASE_NOTES.md
@@ -1,11 +0,0 @@
-Validator changes:
-* (none)
-
-other code changes:
-* fix bug when converting positiveInt between versions
-* fix bug raising error when processing bundles
-* don't use prism for big binaries when rendering library
-* fix parameters renderer to create proper anchors 
-* Don't render id/base/other properties of Resource itself in auto-narrative generator
-* fix bug where extension values not generated for simple extensions
-* fix bug rendering content references in profiles
diff --git a/org.hl7.fhir.convertors/pom.xml b/org.hl7.fhir.convertors/pom.xml
index 91d1bb766..d1d3cd7f8 100644
--- a/org.hl7.fhir.convertors/pom.xml
+++ b/org.hl7.fhir.convertors/pom.xml
@@ -5,7 +5,7 @@
     <parent>
         <groupId>ca.uhn.hapi.fhir</groupId>
         <artifactId>org.hl7.fhir.core</artifactId>
-        <version>5.1.20</version>
+        <version>5.1.21-SNAPSHOT</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/org.hl7.fhir.dstu2/pom.xml b/org.hl7.fhir.dstu2/pom.xml
index 8a6f61054..50bf1db0d 100644
--- a/org.hl7.fhir.dstu2/pom.xml
+++ b/org.hl7.fhir.dstu2/pom.xml
@@ -5,7 +5,7 @@
 	<parent>
 		<groupId>ca.uhn.hapi.fhir</groupId>
 		<artifactId>org.hl7.fhir.core</artifactId>
-		<version>5.1.20</version>
+		<version>5.1.21-SNAPSHOT</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
 
diff --git a/org.hl7.fhir.dstu2016may/pom.xml b/org.hl7.fhir.dstu2016may/pom.xml
index 456c2daa8..cb520f546 100644
--- a/org.hl7.fhir.dstu2016may/pom.xml
+++ b/org.hl7.fhir.dstu2016may/pom.xml
@@ -5,7 +5,7 @@
 	<parent>
 		<groupId>ca.uhn.hapi.fhir</groupId>
 		<artifactId>org.hl7.fhir.core</artifactId>
-		<version>5.1.20</version>
+		<version>5.1.21-SNAPSHOT</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
 
diff --git a/org.hl7.fhir.dstu3/pom.xml b/org.hl7.fhir.dstu3/pom.xml
index 6ace225c3..da94f2fe6 100644
--- a/org.hl7.fhir.dstu3/pom.xml
+++ b/org.hl7.fhir.dstu3/pom.xml
@@ -5,7 +5,7 @@
     <parent>
         <groupId>ca.uhn.hapi.fhir</groupId>
         <artifactId>org.hl7.fhir.core</artifactId>
-        <version>5.1.20</version>
+        <version>5.1.21-SNAPSHOT</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/org.hl7.fhir.r4/pom.xml b/org.hl7.fhir.r4/pom.xml
index e750f415a..dde7ecaa6 100644
--- a/org.hl7.fhir.r4/pom.xml
+++ b/org.hl7.fhir.r4/pom.xml
@@ -5,7 +5,7 @@
 	<parent>
 		<groupId>ca.uhn.hapi.fhir</groupId>
 		<artifactId>org.hl7.fhir.core</artifactId>
-		<version>5.1.20</version>
+		<version>5.1.21-SNAPSHOT</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
 
diff --git a/org.hl7.fhir.r5/pom.xml b/org.hl7.fhir.r5/pom.xml
index a96750963..99fc53216 100644
--- a/org.hl7.fhir.r5/pom.xml
+++ b/org.hl7.fhir.r5/pom.xml
@@ -5,7 +5,7 @@
 	<parent>
 		<groupId>ca.uhn.hapi.fhir</groupId>
 		<artifactId>org.hl7.fhir.core</artifactId>
-		<version>5.1.20</version>
+		<version>5.1.21-SNAPSHOT</version>
 		<relativePath>../pom.xml</relativePath>
 	</parent>
 
diff --git a/org.hl7.fhir.report/pom.xml b/org.hl7.fhir.report/pom.xml
index eca8eb2a6..fa7b2b286 100644
--- a/org.hl7.fhir.report/pom.xml
+++ b/org.hl7.fhir.report/pom.xml
@@ -5,7 +5,7 @@
     <parent>
         <groupId>ca.uhn.hapi.fhir</groupId>
         <artifactId>org.hl7.fhir.core</artifactId>
-        <version>5.1.20</version>
+        <version>5.1.21-SNAPSHOT</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/org.hl7.fhir.utilities/pom.xml b/org.hl7.fhir.utilities/pom.xml
index d5e1b87dd..d6da0d28c 100644
--- a/org.hl7.fhir.utilities/pom.xml
+++ b/org.hl7.fhir.utilities/pom.xml
@@ -5,7 +5,7 @@
     <parent>
         <groupId>ca.uhn.hapi.fhir</groupId>
         <artifactId>org.hl7.fhir.core</artifactId>
-        <version>5.1.20</version>
+        <version>5.1.21-SNAPSHOT</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/org.hl7.fhir.validation.cli/pom.xml b/org.hl7.fhir.validation.cli/pom.xml
index 7727cb7e8..849541b16 100644
--- a/org.hl7.fhir.validation.cli/pom.xml
+++ b/org.hl7.fhir.validation.cli/pom.xml
@@ -5,7 +5,7 @@
     <parent>
         <groupId>ca.uhn.hapi.fhir</groupId>
         <artifactId>org.hl7.fhir.core</artifactId>
-        <version>5.1.20</version>
+        <version>5.1.21-SNAPSHOT</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/org.hl7.fhir.validation/pom.xml b/org.hl7.fhir.validation/pom.xml
index bc0bd3785..7ad6a3959 100644
--- a/org.hl7.fhir.validation/pom.xml
+++ b/org.hl7.fhir.validation/pom.xml
@@ -5,7 +5,7 @@
     <parent>
         <groupId>ca.uhn.hapi.fhir</groupId>
         <artifactId>org.hl7.fhir.core</artifactId>
-        <version>5.1.20</version>
+        <version>5.1.21-SNAPSHOT</version>
         <relativePath>../pom.xml</relativePath>
     </parent>
 
diff --git a/pom.xml b/pom.xml
index dad1a8526..c1c73023a 100644
--- a/pom.xml
+++ b/pom.xml
@@ -14,7 +14,7 @@
     HAPI FHIR.
     -->
     <artifactId>org.hl7.fhir.core</artifactId>
-    <version>5.1.20</version>
+    <version>5.1.21-SNAPSHOT</version>
     <packaging>pom</packaging>
 
     <properties>