diff --git a/bindings/nostr-sdk-ffi/src/protocol/event/tag/standard.rs b/bindings/nostr-sdk-ffi/src/protocol/event/tag/standard.rs
index 0cd6f9062..bb371c288 100644
--- a/bindings/nostr-sdk-ffi/src/protocol/event/tag/standard.rs
+++ b/bindings/nostr-sdk-ffi/src/protocol/event/tag/standard.rs
@@ -110,6 +110,8 @@ pub enum TagStandard {
     },
     Kind {
         kind: KindEnum,
+        /// Whether the k tag is an uppercase K or not
+        uppercase: bool,
     },
     RelayUrl {
         relay_url: String,
@@ -355,7 +357,10 @@ impl From<tag::TagStandard> for TagStandard {
             tag::TagStandard::ExternalIdentity(identity) => Self::ExternalIdentity {
                 identity: identity.into(),
             },
-            tag::TagStandard::Kind(kind) => Self::Kind { kind: kind.into() },
+            tag::TagStandard::Kind { kind, uppercase } => Self::Kind {
+                kind: kind.into(),
+                uppercase,
+            },
             tag::TagStandard::Relay(url) => Self::RelayUrl {
                 relay_url: url.to_string(),
             },
@@ -550,7 +555,10 @@ impl TryFrom<TagStandard> for tag::TagStandard {
                 coordinate: coordinate.as_ref().deref().clone(),
                 relay_url: relay_url.map(UncheckedUrl::from),
             }),
-            TagStandard::Kind { kind } => Ok(Self::Kind(kind.into())),
+            TagStandard::Kind { kind, uppercase } => Ok(Self::Kind {
+                kind: kind.into(),
+                uppercase,
+            }),
             TagStandard::RelayUrl { relay_url } => Ok(Self::Relay(UncheckedUrl::from(relay_url))),
             TagStandard::POW { nonce, difficulty } => Ok(Self::POW {
                 nonce: nonce.parse()?,
diff --git a/crates/nostr/src/event/builder.rs b/crates/nostr/src/event/builder.rs
index 05f124a2e..3925f6de9 100644
--- a/crates/nostr/src/event/builder.rs
+++ b/crates/nostr/src/event/builder.rs
@@ -526,9 +526,10 @@ impl EventBuilder {
                 uppercase: true,
             }));
             // Kind
-            tags.push(Tag::from_standardized_without_cell(TagStandard::Kind(
-                root.kind,
-            )));
+            tags.push(Tag::from_standardized_without_cell(TagStandard::Kind {
+                kind: root.kind,
+                uppercase: true,
+            }));
 
             // Add others `p` tags
             tags.extend(
@@ -554,9 +555,10 @@ impl EventBuilder {
             uppercase: false,
         }));
         // Add `k` tag of event kind
-        tags.push(Tag::from_standardized_without_cell(TagStandard::Kind(
-            reply_to.kind,
-        )));
+        tags.push(Tag::from_standardized_without_cell(TagStandard::Kind {
+            kind: reply_to.kind,
+            uppercase: false,
+        }));
 
         // Add others `p` tags of reply_to event
         tags.extend(
@@ -680,7 +682,10 @@ impl EventBuilder {
                         uppercase: false,
                     }),
                     Tag::public_key(event.pubkey),
-                    Tag::from_standardized_without_cell(TagStandard::Kind(event.kind)),
+                    Tag::from_standardized_without_cell(TagStandard::Kind {
+                        kind: event.kind,
+                        uppercase: false,
+                    }),
                 ],
             )
         }
@@ -743,7 +748,10 @@ impl EventBuilder {
         tags.push(Tag::public_key(public_key));
 
         if let Some(kind) = kind {
-            tags.push(Tag::from_standardized_without_cell(TagStandard::Kind(kind)));
+            tags.push(Tag::from_standardized_without_cell(TagStandard::Kind {
+                kind,
+                uppercase: false,
+            }));
         }
 
         Self::new(Kind::Reaction, reaction, tags)
diff --git a/crates/nostr/src/event/tag/standard.rs b/crates/nostr/src/event/tag/standard.rs
index ad205b3a7..5278361b3 100644
--- a/crates/nostr/src/event/tag/standard.rs
+++ b/crates/nostr/src/event/tag/standard.rs
@@ -103,7 +103,11 @@ pub enum TagStandard {
         coordinate: Coordinate,
         relay_url: Option<UncheckedUrl>,
     },
-    Kind(Kind),
+    Kind {
+        kind: Kind,
+        /// Whether the k tag is an uppercase K or not
+        uppercase: bool,
+    },
     Relay(UncheckedUrl),
     /// Proof of Work
     ///
@@ -308,10 +312,6 @@ impl TagStandard {
                     character: Alphabet::D,
                     uppercase: false,
                 }) => Ok(Self::Identifier(tag_1.to_string())),
-                TagKind::SingleLetter(SingleLetterTag {
-                    character: Alphabet::K,
-                    uppercase: false,
-                }) => Ok(Self::Kind(Kind::from_str(tag_1)?)),
                 TagKind::SingleLetter(SingleLetterTag {
                     character: Alphabet::M,
                     uppercase: false,
@@ -509,9 +509,9 @@ impl TagStandard {
                 character: Alphabet::A,
                 uppercase: false,
             }),
-            Self::Kind(..) => TagKind::SingleLetter(SingleLetterTag {
+            Self::Kind { uppercase, .. } => TagKind::SingleLetter(SingleLetterTag {
                 character: Alphabet::K,
-                uppercase: false,
+                uppercase: *uppercase,
             }),
             Self::Relay(..) => TagKind::Relay,
             Self::POW { .. } => TagKind::Nonce,
@@ -693,7 +693,7 @@ impl From<TagStandard> for Vec<String> {
                 vec
             }
             TagStandard::ExternalIdentity(identity) => identity.into(),
-            TagStandard::Kind(kind) => vec![tag_kind, kind.to_string()],
+            TagStandard::Kind { kind, .. } => vec![tag_kind, kind.to_string()],
             TagStandard::Relay(url) => vec![tag_kind, url.to_string()],
             TagStandard::POW { nonce, difficulty } => {
                 vec![tag_kind, nonce.to_string(), difficulty.to_string()]